time recording terminal can't connect through explicit proxy

[manuelm]

We are trying to establish an HTTPS connection to the Internet for a time recording terminal via Fortigate explicit proxy. In packet capture we recognize that data is arriving. But we don't see anything in Logs or FortiView. It appears that Fortigate is being discarded the data. The manufacturer of the time recording devices only sees that Fortigate closes the connection (FIN, Ack). Otherwise, the explicit proxy works with hundreds of PCs without any problems. What else could I do to find out why the connection isn't being established? 

Thanks in advance

We use Fortigate v7.4.2 build2571

[AEK]

The below tech tip should help to debug the proxy.

https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-debug-the-web-proxy-and-explicit-pr...

[manuelm]

I have already tried this. I can't use this command: diagnose wad debug-url enable
This is not available. But i can't find anything comparable.