Not getting advertised 2Gbps speeds

I recently signed up for the 2Gbps down/ 1gbps up service  . Cox sent me their PW8 modem to use but I am using my own TP Link BE9300 router which supports 2.5 Gbps out of the box. I did a speedtest but I'm not getting the advertised speeds. I tried switching modems , using different ethernet cables, used different computer, I even tried connected it directly to the ONT. But my speedtest is not getting more than 1Gbps. I already chatted with CS but it wasn't helpful.