We have created a temporary 3cx (V11) server that is going to be used for a disaster recovery test. We have created the server from a backup of the production 3cx server , we are using provisioning to provision 9 Yealink T28 phones to 9 new extensions that are only be used for the test. The provisioning has worked well and all phones have registered without any problems. For the purpose of the test we only need to make internal calls, however although the phones can make calls no problem there is no audio at either end of the call. Anybody any ideas?