Same issue here, also fixed it by using 5.12
Posts made by berko
RE: Centos 7 login problem after updating mono to 5.14
Error With Token API
I've updated my Ubuntu 16.04 machine, which updated Mono to 5.14.
After this, i was getting "Error With Token API" when trying to login.
After some debugging i could not figure out why it failed, but when uninstalling mono, and installing 5.12 instead, everything worked out just fine.
Log from error with 5.14 is attached.