So if I was you this is what I would try.
Download a copy of this MiniWeb and run it on the same PC.
(If you have something else on port 80 already use a different port like 8080 or 8888)
Once that is up you should be able to browse to http://192.168.1.24 and see the default miniweb blue page
Setup a new port forward on your TP-Link Archer VR600 for port 80 or whatever port you specified
Note: Port 80 is reserved on the TP-Link https://www.tp-link.com/us/faq-72.html
So might be best to use like 8080 or something else
go to canyouseeme.org and verify this new port shows Success
This will eliminate Plex as being the issue if it also does not show Success.
Only other thing in line would be your local OS FIrewall…
The port it opened is 8000.
When browsing to http://192.168.1.102:8000/, I got the blue page you’ve mentioned.
Then, I mapped is as follows:
Following which, I paused Kaspersky, and added rules to the Win10 firewall to allow both 8080 and 8000 (just in case, both inbound and outbound).
In http://canyouseeme.org/ - connection is still being refused.
So, what am I missing? When Kaspersky is paused, Windows firewall both disabled AND configured to allow these ports, something is still refusing the connection. What could this possibly be?