2021 m1 MacBook Pro External monitor 30Hz

First of all, please understand that my English is not good because I use a translator.

I am using a MacBook with only a Thunderbolt 3 cable (clamshell mode).

But the problem is that the MacBook has its refresh rate fixed at 30Hz.

Even if you use the genuine C type cable provided by LG,

it is fixed at 30Hz, and even if you use a certified Thunderbolt cable, it is still fixed at 30Hz.

The only option to change to 60Hz in EasyRes is low quality mode.

And I have already reset the monitor several times.

What should I do to fix this?

I've already spent dozens of hours on this problem.

The current configuration is as follows.

External monitor: LG 27UK670

Connection status: Connected directly from the monitor to the MacBook using a Thunderbolt 3 cable without any hub. (Brand: ACON)

Power: supplied from monitor via Thunderbolt3 cable (40w)