Two errors - 0:521 and must launch Adobe prompt

Our version is 22.1.20085.0 and we've encountered two issues recently while attempting to download & open PDF files.  I've attached the error messages.

On one system we received a 0:521 error message with 'please launch Adobe acrobat...' and the other one was for us to launch Adobe reader first.  We're using the product as a PDF viewer and have encountered these two errors out of 110 tests.  Our software is calling for a PDF to be downloaded and viewed locally.  I have not been able to replicate the issue and I'm not familiar with the logging, if any, involved.  I see nothing noteworthy in the Windows Event logs.