As part of the merger, ZBrush subscription licences have been moved to the MyMaxon account.
Emails have been sent to the email address on record to inform users of this and the instructions necessary to continue using, please check any SPAM and Junk mails to see if you had not received them.
Your old ZBrush installation (up to 22.0.5) may have been in its 14-day grace period after the licence was moved.
To resolve this, please download the Maxon App from the link below;
And log in with your new MyMaxon account - which should be the same email as your old Pixologic account.
Once logged in, please install the ZBrush available, as this will be the updated version that works with the MyMaxon accounts.
If you still require further assistance, please raise a ticket.