martinus-Amember Kindly ensure if you had followed the documentation excerpts for upgrade instructions whilst updating the specific template
Also, As mentioned on the similar page, You must have taken backup which is always quite necessary in case rollback is needed :
Take a full backup
Please always make a back-up before proceeding to any of the upgrade process. In case there is any problem, you can always restore from the back-up files.
Kindly elaborate exactly what all changes, modifications or customizations done to the template arent reflecting ?