Thanks for checking that.
If you take the USB stick back home to the machine that did the export, then fully exit Opus (via File / Exit Directory Opus) so the installed copy is not running in the background, and then run the USB copy, does that work OK?
(After launching the USB copy, type /home into the location field to confirm you're definitely running it from the USB stick. It should take you to where the current running version is located.)
If it works on one machine but not another, using the same USB stick and same data on the stick, then my guess is that something on the work machine is making it appear to be a different USB stick which Opus doesn't recognise as the one the export was written to. e.g. Some corporate environments run things that make USB sticks read-only, which perhaps could cause something similar (although not usually or before now, in my experience at least).
If it does not work even on the machine at home, it's worth trying to do another export in case something went wrong the first time. Please also try the non-dongle mode in case that behaves differently, which might provide a direction to investigate further.