Critical Error

@kalusha – is this the plugin you’re using? WP-Members

I’ve installed that plugin and played around with it to try to reproduce the error. Everything appears to be working fine with both the default /wp-login.php?action=register form and the in-page register form for restricted pages.

If you can provide the exact error message to me or @robin-w we may be able to make Style Pack work with the WP-Members plugin.

Enabling Debugging may help you get the error. You can temporarily enable debugging by adding the following lines to your wp-config.php file:

define( 'WP_DEBUG', true );

// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );

// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', true );
@ini_set( 'display_errors', E_ALL );

define( 'SCRIPT_DEBUG', true );

And for better control over debug messages, I recommend this plugin – DebugPress

403 error means “forbidden”

Follow the official documentation for how to add that debugging code to wp-config.php:

Debugging in WordPress

Probably related to this:

NOTE: You must insert this BEFORE/* That's all, stop editing! Happy blogging. */ in the wp-config.php file.

Also, by default

define( 'WP_DEBUG', false );

is already there. You can delete that line or comment it out and then paste the code I gave you in the same spot.

@robin-w – If that function for subscription management deals with user registration in any way (original critical error reason), then it’s certainly a possibility. If not, then I suspect the issue will still exist.