Hi there!
Thanks for contacting us.
Our Helix3 framework got Joomla 4 compatibility update, so there is a huge transformation this time. We will update all our helix3 based templates soon to make them compatible with the new version of Helix3 framework as well as the Joomla 4.
As you can see the Tixon template doesn't get updated recently:
https://prnt.sc/26c68hx
https://prnt.sc/26c68nw
So, please roll back to your last working backup and kindly don't update your helix3 system plugin until the template gets an update.
Best Regards