[SOLVED] Template COOLNESS in Nirvana

Good morning,
expecting somebody can help at this problem.
On homepage 2 templates ve been installed - one Jsn and Coolness. Coolness for the CB Community-work. CB Communities with all the CB programms CB, GroupJive and CBSubs.
During the past months we could establish the programms easy, running well.
2 weeks ago the Coolness-template could not be activatet in frontend.
No other 3rd party-extension or plugin have been installed in the meantime. Only updates from CB-programms have been installed.
If Coolones is the standard template, it reacts normal.
We checked all the menues, modules and plugins, they are all correct maintained.
What could be the reason, we donot touched the cms or else.
Thank you for any assistance.
PL

Template assignment is entirely powered by Joomla. The template it self and CB have no control over it. Joomla loads templates based off module assignment or template switcher. Best I can suggest is disable all SEF and review the Itemid in your URL then compare it to its Joomla menu item to ensure template assignment is setup correctly.

Thank you - this error started when I was ready with the all GroupJive configurations, and I ve gone through the yours video instructions. There I made a mistake, in the categories config. I will start again to configure GJ. (On 2 other (similar)plattform configuations since January we have not these artificial configs and they are running well.) Thank you
PL