Special:UserRights is no longer allowing to extend an userright without removing the relevant right first, when changing user rights for users on foreign wikis. A notification is triggered saying the rights were successfully changed, but nothing does change, and no log is generated either.
I tried multiple times, using the predefined "1 year", or by manually inserting a one-year time.
Earlier this year @Urbanecm managed to do it for the same user, so something changed in the meantime:
14:03, 13 April 2020 Martin Urbanec (A/S) talk contribs block changed group membership for Gcd822@kowikiversity from administrator (temporary, until 17:42, 13 April 2020) to administrator (temporary, until 14:03, 13 October 2020) (per request: renew) (thank)
Current expiration time: Member of: Administrators (until 14:03, 13 October 2020)