Request to Quickpay using TLS 1.1 will be rejected starting from the 1st of April 2020.
TLS is a protocol used in the encryption between for instance a server and a browser. TLS 1.2 or 1.3 is strongly encouraged by PCI.
Read more on TLS on wikipedia https://en.wikipedia.org/wiki/Transport_Layer_Security
From the 1st of April, you can no longer communicate with our systems or accept payments if you are still using TLS 1.1.
Most likely this will not be a problem, as the majority of systems already use TLS 1.2 or 1.3. However, we recommend that you as soon as possible contact your web hosting service to confirm that your systems are updated.