I am not always online. Here’s some tips about your issue:
First, to regain control of your site, you can delete the plugin directory. In this case it would be wp-content/plugins/wallets-cp. After deleting this directory you should regain control of your site. If you need to delete the parent plugin as well, it is in wp-content/plugins/wallets. You will not lose any data related to the plugin.
If you like to try again, you can try the following:
1. Switch to a standard theme. Install the CoinPayments adapter again. Does it work this time? Some themes improperly enqueue the TGMPA library, causing issues with other plugins that use the same library. If installation works with the other theme, then delete the file wp-content/plugins/wallets-cp/includes/third-party/class-tgm-plugin-activation.php and try your original theme again.
2. If the above fails, I would recommend that you enable WordPress debugging. Then, once the 500 error is caused, the error will be written out to wp-content/debug.log. Please send me the error message if you find it.