Intergration code no longer works

[aquiss]

Good Morning,

The past 2-3 days we have been getting calls and emails from customers saying they can't log into our website via the Integration button that has worked for years (code below).

Baffled by this, I've spent this morning trying to work out what's going on. On testing, it appears that Google Chrome and Edge (based on Chrome engine) literally just refresh the page and don't login. However, other browsers, such as older Internet Explorer, work just fine. I can only presume Chrome has pushed out an update very recently?

<form method="post" action="URLSNIPPED/dologin.php">
<input type="hidden" name="username" size="50" value="<?php echo "$email";?>">
<input type="hidden" name="password" size="20" value="<?php echo "$custpassword";?>">
<input type="submit" class="button button4" value="Setup Your Payment - Pay Now">

Is there a solution to solve this or is there a better way that I can provide a login means for someone to login to the client portal via an alternative integration method?