Hi Stefan, welcome.
Which application throw the error 91 (not seem a Voyager error)?
Please send an email with log to support email.
If you start before midnight Voyager please send also the log of day before.
https://voyager.tourstar.net/index.php?title=Installation#Log_File
You have in anycase the remote assistance with teamviewer or anydesk if you need.
All the best
Leo