API V8 - fatal error


I am currently trying to check out the V8 API, but I can’t set it up due to a fatal error in oAuth2 Clients and Tokens.
I have set display_errors = false in php.ini, however the problem is still present. I checked as well the permissions of the Windows folders, to my understanding they should have enough permissions assigned.
I am using Windows 10.
Does anyone have an idea what may be the cause for this error or can give me a hint where to check specifically?

When I open Admin > oAuth2Clients and Tokens I get 2 notices
" Notice: Undefined index: name in C:\wamp64\www\SuiteCRM\include\SearchForm\SearchForm2.php on line 633"
" Notice: Array to string conversion in C:\wamp64\www\SuiteCRM\include\ListView\ListViewData.php on line 546"
when I click on Create the fatal error
“Fatal error: Smarty error: [in cache/themes/SuiteP/modules/OAuth2Clients/EditPassword.tpl line 128]: syntax error: unrecognized tag ‘main’ (Smarty_Compiler.class.php, line 585) in C:\wamp64\www\SuiteCRM\vendor\smarty\smarty\libs\Smarty.class.php on line 1100

Sadly uploading the screen shots doesn’t work for new users.

Thanks in advance