Cannot Login To Client Area After Upgrade to 7.8.3

[Eezwan]

Hello

I cannot log in to the client area after upgrade to 7.8.3. Every time I log-in to the client area it gives me this error:

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Error: Call to undefined function WHMCS\getClientDefaultCardDetails() in /home/sites/8a/7/76a3770144/public_html/billing/vendor/whmcs/whmcs-foundation/lib/Client.php:0
Stack trace:
#0 /home/sites/8a/7/76a3770144/public_html/billing/vendor/whmcs/whmcs-foundation/lib/ClientArea.php(0): WHMCS\Client->getDetails()
#1 /home/sites/8a/7/76a3770144/public_html/billing/clientarea.php(0): WHMCS\ClientArea->initPage()
#2 {main}

[zomex]

I would first recommend checking under WHMCS admin > help > System Health Status. Make sure there's no errors or warnings here.

Are you using a custom template? If so try testing using the default Six template to see if you can narrow down the problem. If Six is also causing the same error check to see if you're using any 3rd party modules/hooks, although these errors point to WHMCS files it could be triggered by a problematic mod.