if your payment gateway in WHMCS dont mark invoices as Paid or after clicking Pay button it even dont show payment gateway (blank page or error: Fatal error: Call to undefined function gettokenmanager() in /home/whmcs/public_html/clients/dbconnect.php on line 0 ), the issue might be same as i had.

I might wrong updated WHMCS or im not sure,

but i just needed to replace old include format like WHMCS says:

Please check and ensure that your dbconnect.php file is the correct version for WHMCS 5.2.12. From the description, it would suggest the file is an older version.

Within your callback file, you can replace the following code:




Which is the new method and will load the required information for you also.
Just lookup your payment files in /modules/gateways/, /modules/gateways/callback and possilby /modules/gateways/yourgateway and search for line containing "dbconnect.php" and do above mentioned replacement.

So you need to check your gateway module files in /modules/gateways and /modules/gateways/callback and make sure to replace 4 includes by 3 lines mentioned as above. First backup original file.

PS: In case you have this error while loading file in root directory of WHMCS installation, then require("../../../init.php"); will be require("init.php");

WHCMS Modules that failed and needed FIX:
- Payeer.com WHMCS payment gateway module
- CoinPayments.com WHMCS payment gateway module