Plugin edit settings error

[Ioannis D]

I've successfully installed Tapatalk plugin and I have a white page with HTTP ERROR 500 when I want to edit the settings in order to apply my API Key from Tapatalk.

From cPanel I can choose PHP versions, now I have PHP 5.6, when I change to PHP 7 and try to edit again the plugin settings it appears a pop-up message with this content "Something went wrong. Please try again.".

Does anyone have the same issue or had and it solved? I've already submitted a support ticket to Tapatalk but I don't know if it's theirs issue or it's from my installation.