Error: Registration server returned '' (403)

Hello,

I would like to upgrade a Linux server from SLES 15 SP4 to SLES 15 SP5.
After executing "zypper migration" following error is displayed:

All repositories have been refreshed.
Executing '/usr/bin/zypper --disable-repositories --xmlout --non-interactive products -i'
Can't determine the list of installed products: Error: Registration server returned '' (403)
'/usr/lib/zypper/commands/zypper-migration' exited with status 1


After call status it brings following:

# SUSEConnect --list-extensions
Error: Registration server returned '' (403)
# SUSEConnect --status
Error: Registration server returned '' (403)

Does somebody know what it means? Is there any issue with SUSE server?

Thank you!
Regards,
DieSuseSusi