Indirect playback for MacOs laptop with Plex server issue

I always had issues connecting with my MacBook Air 2020 M1 to my windows 11 based desktop Plex Server. I face the issue with the Mac Plex app, the safari browser, and Chrome, when I try to access my Plex Server. I don't have an issues accessing the server with its ip and port from my Mac though, from any browser(ip+port as a browser address). It's like something is blocking the connection from my MacBook and I have this issue with the Mac apps. I have a modem/router provided by the ISP which I suspected had an issue with connecting to too many wifi devices at the same time and assigning correct IPs. So, I created a port forwarding which made Plex to work even on my MacBook. I thought that having an open port in my crappy Chinese made ISP modem/router isn't the safest thing, so I bought a router which I connected to my ISP modem/router. I closed the Port forwarding and I deactivated the WAN transmission from my ISP modem and set up my new TP Link router for my wifi. Everything works just fine. Plex works just fine in all devices (windows 11 pc, Nvidia Shield, Xiaomi Mi Box, Xiaomi Poco android phone) but still doesn't work on my MacBook (besides accessing the server directly on a browser as ip+port number/web). Keep saying that it's an indirect connection and when I'm trying to watch something from that server it only plays it in a very low quality. My Nvidia Shield also acts like a server too and from my MacBook or any other of my devices I don't have any issues accessing media from it in full quality and directly. What can be wrong with my Plex setup or my MacBook Air?

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