802.11r Fast Roaming - Limited Connectivity, needs reconnecting

I have 21.02 installed on a TP-Link Archer A6 and Xiaomi Mi 4A Gigabit. 802.11r was working fine for some time but now I have a weird issue. If I roam from one floor to another, the internet becomes "Limited" with no network access.

I use a TP-Link R600 multi-WAN wired VPN Router. How can I resolve or diagnose the issue? Help, please.

"Limited" is probably your OS saying it has a working wifi link but it can't access the internet through that link.

Are you on a laptop? Run wireshark on the wifi interface and see if something interesting happens during this transition time. Random guess: are the two wireless access points running on different IP ranges, so your device has to DHCP all over again?