This error may happen from time to time on older SAP versions. It is random in nature and there is no known fix outside of upgrading to the latest version of SAP where it seems to occur less frequently.
The issue is with the SAP UI API that sends an incorrect token when launching the add-on.
There is, unfortunately, nothing we can do to solve/workaround this issue as it is due to a bug in the SAP client.
Based on our experience such error can also occur on these circumstances:
1. SAP components are allowed to connect to the SAP database server, but Boyum components are blocked by the firewall.
2. SAP Client is installed with insufficient privileges / the client is corrupted. You can re-install the SAP Client with "Run as administrator" -mode and with antivirus/antimalware software disabled.
3. If the environment has strict internet policies or no internet connection at all, please try and follow this article and see if that fixes it: https://support.boyum-it.com/hc/en-us/articles/360026119714-B1UP-is-slow-time-out-starting-in-a-system-with-no-internet-or-very-strict-Internet-policies
This is a list of fixes we've got from our partners after contacting SAP, please contact SAP support if none of them help.