Although the login is successful, the members see a page with a red "something went wrong". By refreshing the page, and in extreme cases by going to the homepage, everything starts working again. The error log is replete with:
RE: Array ( [error] => httpServerError [error_description] => Invalid grant: authorization code has expired )
Grant authorization time is 30 seconds. It would be impossible for the grant to have expired during login (3-4 seconds max). The date/time on the machine is 100% accurate.
Please advise.
With kind regards,
Michel