I have found a problem with the session key variable name which stopped this module working with a contribution for multiple prices per customer group I have been using.

Ammend line 58 in the callback script onwards from:

foreach($array as $kn => $v) {
global $$kn;
$_SESSION[$key] = $$kn = $v;
}

to:

foreach($array as $kn => $v) {
global $$kn;
$_SESSION[$kn] = $$kn = $v;
}

Simple mistake, hope that helps.

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