After I upgraded from ATA 3.6.4 to the new version 3.7.1 my search doesn't work anymore:

Fatal error: Maximum execution time of 90 seconds exceeded in /var/www/domain.com/wp-content/themes/atahualpa/functions.php on line 296

what is the url?
who is the host?
do other functions work?
How big is the database (how many posts)
when was the last time you optimized the db?

It seems to have to do with the plugin Relevanssi. When I deactivate it, the search runs fine again. When I activate it, after a long time of waiting the error message above occured. Before the upgrade I didn't had such problems. Both, Atahualpa and Relevanssi worked fine together. So what to do now? Was there any change in the new ATA version that might cause this error?

have you built the index. I wonder if changing themes (an update is seen by wordpress as changing the theme) cause an index issue with the plugin.

Of course I have build the index. I also uninstalled and deleted the plugin and installed it anew, but nothing changes...

I just tested it on my site and it works fine.
can you answer my questions from post #2