What could be wrong with my (TP-LINK 1042 + OpenWRT) router?

Question

network hardware

Everything worked before. I also made a backup of the router.
I can't send files on telegram. (you have to open the web version)
You can log in to League of Legends, but not the first time.
From the router I get everything automatically. The Internet is working. Router settings are normal. There is IPv6.
Why attention fell on the router, because in the same provider network in another place with IPv6, I can easily send files and log into the game.
At home there are other devices, phones, laptops. They do not experience problems with data transfer and authorization in the game.
I have Win10.

Answer 1

where exactly are you trying to get - are telegrams and League of Legends reachable from you via ipv6?
file exchange exactly happens on ipv6 in other cases?
do you only have ipv6 or do you have v4 as well?
ipv6 native or tunnel?
v4 address is gray or behind a provider's nat?
Are the ipv6 settings from the router up to date?
is your provider giving you an ipv6/dhcpv6 subnet? If so, are all settings correct?
whether there are no statically set addresses?
you can also try to simply reset the ipv6 settings on a specific computer - right-click on start, command line (administrator), netsh int ipv6 reset c:\reset.log