It might be permission related, and it probably is, but in a very convoluted way.
Here is some background:
There are multiple versions of UA certificate generator "in the wild", with difference(s) in the syntax (-hashSize among them).
QuickOPC comes with an embedded binary of UA certificate generator which it tries to use - this assures that the syntax is always right, because we would be calling the version for which we have written the code.
But the process of running this "embedded" UA certiticate generator executable *does* require some permissions (such as for placing files on disk).
If it fails, there should be something in the QuickOPC logs (EasyUAClient.LogEntry) I believe, and a "standard" procedure for location UA certificate generator kicks in, looking for preexisting file at multiple places in the file system. it is possible that this then finds a version of the UA certificate generator that was already there (e.g. installed by other OPC UA product), but is different from what we expect.
Possible solutions might be:
1. Give the process enough permissions. Probably not a good idea under IIS, for security reasons.
2. Replace the version on disk with the right version (I may help with that).
3. Generate the certificate manually upfront, and have your app simply use it, without generating it automatically by itself (there should be instructions for this in the User's Guide).
Best regards