Problem with WIND 3g connection and Let's Encrypt certificate

accountservergroup.com it is connected with the hosting site5.com.
And how could I explain to wind3 customer care this problem??? I 'll try

SSL checker says:

The certificate is installed correctly.

Information about the certificate

DV

This server uses a Domain Validated (DV) certificate. No information about the site owner has been validated. Data is protected, but exchanging personal or financial information is not recommended.

Common name: teatrosanteodoro.it
SAN: teatrosanteodoro.it, www.teatrosanteodoro.it

Valid from: 2021-12-30 08:56:07
Valid to: 2022-03-30 08:56:06

Certificate status: Valid
Revocation check method: OCSP