From experience there are many significant changes made to each new version of Prestashop, PHP, and Barclaycard's integration platform that could all impact upon the correct working behaviour of the module introducing bugs or compatibility issues unless the module is maintained and software updates made available to you.
Have you upgraded your Prestashop version or PHP version recently? If so, do you have a working backup you could return to or compare with?
Since this is a commercial software product your first port of call should always be to contact the original software vendor for support. There will likely be contact details for the original developers written into the top of source code files or in an accompanying readme.txt file.
You'll be unable to post the source code online in a public forum and so it's unlikely we'll be able to help beyond signposting you to the options available, so with that in mind here are some of the options available to you in the event you are unable to reach the original vendor:
Paid programming support from a web development or hosting company that specialise in PHP development and have experience writing code for and supporting Prestashop installations.
The payment module you currently use for your Barclaycard ePDQ integration will unlikely be the only one available, since add-ons such as this are not usually very expensive you could try a different module from a different software vendor. A google search for "prestashop epdq" should quickly reveal the relevant modules available, though Barclaycard also list a couple of Prestashop software integration partners on their website.
