Hi, after last update, my site is down, I did a change of default theme, it works fine, then I change back to original default theme then I found the theme name is removed in other language so I set again the name in the field, after that I visit my site and it works ok, now I try to login, after did it the site is crashed again... Now it seems works fine as Guest but not for members. 

I did as it recommended, clear cache with support, but nothing. How can I restore that theme? I don't want to just use another default theme, because I will have to invest again time to check which changes and css past into it. 

Is this for the beta version or the latest stable version?  If it’s the beta, it’s because of an issue with the global template. 

https://invisioncommunity.com/index.php?app=core&module=system&controller=plugins&do=diff

You'll see the manual changes you need to make by comparing the stable version to beta. 

IPS says they’ll add it back in next beta temporarily but you’ll want to get your themes updated anyway.