After update, I cannot use the software anymore.
When I want to move a file from one folder to another, the answer is
Access is denied. (5)
When I want to copy from outside, e.g. from Outlook, it says
The system cannot find the file specified. (2)
Then that antivirus is frankly garbage. If it thinks Opus or something Opus is doing is suspicious, it should tell you, not just break things and leave you (and us) to work out why. If there really was malware on your system, you still would not know, because it hasn't warned you. And there is nothing suspicious about what Opus is doing, so it shouldn't be blocking things in the first place.
If your antivirus is breaking software, the issue is with the antivirus (or its configuration). You should complain to the antivirus vendor, and/or change to something better. (As an example, ESET/NOD32 has never caused a problem like this.)
The issue may go away as the new signatures becomes more "trusted", but the unacceptable thing here is the antivirus, not anything Opus is doing. Opus can't function correctly if antivirus is breaking the operating system.
I would like to add that im using the latest WIN10 x64 (2004 19041.572) and i did not experience such issues. Updated DOPUS from the latest beta to 12.22 and windows defender or whatever its called did not block any of the DOPUS functions.
It may depend on the Defender configuration and/or the contents of the files being copied.
A lot of "privacy" options in antivirus will block software (other than File Explorer) from opening files that contain things like your email address or numbers that look like a credit card.
(Allowing Explorer through makes the whole protection somewhat pointless, since anything that wanted to could easily trigger the copy inside of explorer.exe via various well-known methods.)
You can usually whitelist Opus, but you may also need to whitelist any other software that deals with those files. And it can block files being opened that don't really contain any private data; just things that look similar. The whole concept causes more problems than it solves, in my opinion, but we have no control over it. We ask to open a file; antivirus may intervene and fail the request, and all we can do is report that it failed.
If Defender decides it doesn't like our process, or it doesn't like a process opening particular files, then we literally cannot do anything about that.
We ask the operating system to open a file, and the request fails, because the antivirus makes it fail. We have zero control over that. The antivirus has total control over it. We could retry the request, but it would only fail again. The antivirus has put itself between us and the file, and won't get out of the way.
You need to do one of:
Work out how to configure the antivirus to make it not block Opus when it accesses those files.
(Working out which files or file types it's blocking may provide a clue there. For example, if they're files that contain your name and address, it may be a "privacy" feature of Defender rather than an antivirus feature.)
Or wait for the new signature to be more well-known.
(Whether that will help or not depends on exactly why the antivirus is blocking access to the files in question, which we can't answer as we didn't write the antivirus.)
Or ask the people whose job it is to make/support the antivirus for advice on why it is blocking things.
(Also ask them why they think it makes sense to block something they feel is suspicious but not tell you about it. It makes no sense to think something is suspicious enough to block, but not suspicious enough to warn you about. And it causes support issues for the rest of the world.)
Or switch to a better antivirus. (Defender is not that good these days, and has been regularly causing people weird problems and performance issues lately.)
We have no control over what Defender does, so we cannot change any of this. The only relevant thing which changed in Opus between the updates is that our code-signing signature was renewed, which happens every three years. (This is normal. Signatures expire and have to be renewed regularly.)
I tested now with different files
all of them have no content but the word "empty".
I copy or move all of them outside of the OneDrive directory, but cannot copy or move to the OneDrive directory nor inside the OneDrive directory from one folder to any other with Dopus. With MS File Explorer no problem.
That depends on whether that problem still happens if Defender is disabled, and if the same action works in Explorer or other software or not.
If disabling Defender makes things work again, which you said was the case with your first problem at least, then Defender is the cause.
Whether that's the case for this second issue, I can't say, but you can easily test that yourself by disabling Defender again.
Given you already know Defender is causing one problem, checking if it's causing another problem seems like a good idea.
We don't make Defender and cannot help much if Defender is breaking the operating system by making requests to do things fail.
If Defender is causing one or both problems then you need to ask the people who make Defender for help, or switch to a better antivirus that doesn't cause random problems.
Defender is blatantly the cause of your first issue, since the problem stopped when you disabled Defender. You can keep posting here in the hope that reality will change and some other solution will appear by magic, but it's not likely. Changing to another antivirus or asking experts in Defender for advice on how to stop it breaking things would be a better use of your time if you want to solve the problem.
We know that Defender is made by Microsoft and their support people are not very helpful, but that doesn't mean we can solve their problems. If they can't support you when their antivirus causes problems, then use an antivirus from a better company.
We cannot solve problems here, or by modifying Opus, that are caused by antivirus that breaks Windows and blocks Opus from doing things which should otherwise work.