Test transactions are failing

I recently contacted Alpha Bank to enable electronic payments for my site. Followed instructions and enabled your plugin. I then added the merchant ID and code and enabled Alpha Bank Gateway and Test Environment.
I then run the test as specified by Alpha Bank with information they provided but test transaction fails (I get back to order confirmation page with the error: “Δυστυχ??, δεν ε?ναι δυνατ? η διεκπερα?ωση τη? παραγγελ?α? σα? καθ?? η τρ?πεζα/?μπορο? απ? του? οπο?ου? ξεκ?νησε ?χει αρνηθε? τη συναλλαγ? σα?. Παρακαλο?με, επαναλ?βετε την αγορ? σα?.”
I then checked code examples provided by Alpha Bank and found some fields that do not appear in your code, like form version (they specify ‘2’) and also this part that puzzles me since they seem to require sha256 encoding for the form, but I found sha1 used in the plugin.

// plugin code
function calculate_digest($input) {
$digest = base64_encode(sha1(($input), true));
return $digest;
}

Example code by Alphabank:

$form_data = implode(“”, $form_data_array);
$digest = base64_encode(hash(“sha256”,$form_data,true));

Additionally, despite the fact that I enabled MasterPass in the WooCommerce settings, it doesn’t seem to be working – not only I still am seeing the notification in the dashboard that I need to enable it, but also when selecting it as a payment method during the test checkout, I don’t get any pop up that should show up, and I’m being redirected to standard Alpha Bank (test) payment URL.

I would appreciate your input on what I need to do now to get this working.
Looking forward to our response,

Best regards,
Kati