In the following advice database-changes have to be made and could be therefore dangerous.
I do NOT take any responsibilities for damages resulting from this advice. You do this AT YOUR OWN RISK!
Perhaps you experienced this problems if you have a XOOPS-system installed for a long and after all the upgrades you have some problems to change templates although automatic update of templates is activated.
Please make a database-backup before!!!!!
Step 1: Log in as admin and go to the system preferences and activate the automatic update of templates and themes. Then go to Administration / Templates.
Step 2: Download the current used templateset.
Step 3: Go to Administration / Modules.
Step 4: Open phpMyAdmin of your XOOPS-database in another browser-tab or -window.
Step 5: Now act fast! EMPTY (NOT DELETE) the tables yourprefix_tplfile and yourprefix_tplsource.
Step 6: Update the system-module first and then generate the system-templates of your used templateset. Update all other modules and generate their templates anew.
Step 7: Unzip the downloaded templateset and upload the templates with the templates-manager.
Step 8: Hope that all is functioning now