Unable to connect to CMS v1.8.13

Hello,

We are using Xibo version 1.8.13 for many years and have recently starting seeing the attached error on only some of our new installations.

Details below :

Cms version : 1.8.13
Player version : v1.8

Funny thing is that we are not seeing this behaviour on all the displays, only some.

Any input will be appreciated

Thanks,