SagePay for 2.4 version

HI,

I'm currently using nopcommerce 3.20 and sagepay plugin for card payments.
I'm receiving 5006 error and it's not clear what is going on.
I tried to contact both SagePay and our hosting provider(Arvixe) but unfortunately we haven't find any solution yet.
I'm using a single page checkout and the ssl certificate is correctly installed.
The funny thing is that it was possible to perform transactions either with the test and live sagepay environment before installing the ssl certificate.
Do you have any clue about how the ssl certificate can affect transactions with sagepay?

Thanks

I did some more tests and disabling the ssl everything is working fine.
As soon as I enable the ssl certificate for the checkout process the 5006 error comes back.
All the ports required by sagePay are whitelisted in the firewall config.
If someone has some idea or knows where the problem can be would be really appreciated.

Thanks

Awesome :)