Cannot assign any phones to extensions

[Alano9909]

When I try to assign any phones to an extension (new or existing), I get error:

Internal Server Error(500)
System.UriFormatException: Invalid URI: The format of the URI could not be determined.

Anyone ever seen this or know what is happening?

thanks
Alan

 

[YiannisH_3CX]

Hello @Alano9909

Did you come from a backup or is this a clean installation?
also what service are you on?
what phones are you trying to add to the extensions?

 

[Alano9909]

It's a clean (and new) installation. Currently it's just a test system, so internal calls only to 3CX Windows, Android and IOS clients, all of which work. The phone we're trying to add is a Yealink T48, but we get the error even if we try to assign an extension to a new device, it still gives the error once you enter (any) mac address. So don't think it is hardware related.