Disconnected due to an authentication error. Please wait a while and try again, or send an error report through our inquiry form. [No.787]

Ran into the same issue, all I had to do was follow what was said above: go to the Xbox Companion Console, click the cog, go to settings, log out. Then go back to PSO2. It'll have you relog in (which will log you back into the Xbox Companion Console) and it worked without a hitch. No need to delete any files at all.

@Pikiri6405 said in Disconnected due to an authentication error. Please wait a while and try again, or send an error report through our inquiry form. [No.787]:

@Ruditate Relog on your xbox companion app

It should be pinned somewhere. It's really important info. Thanks for it btw, just got the same problem.