1440p and 120hz won’t work at the same time for my Xbox one X when I purchased a monitor...

For the Xbox one X you have to choose one or the other reguardless of the monitors specs. Either 1080p at 120hz or 1440p at 60hz. The Series X thats coming in November will support 4k at 120hz at the same time. 👍

I didnt read through all the responses but i thought this same thing when i purchased an 27” Asus monitor to play xbox in 1440p@120hz but it didnt work. After reader deaper into the monitor is seems the monitor only suports higher then 60hz when using
a display port cable, not hdmi. I took the monitor back, it wasn’t the xbox. It works fine with my samsung Q8, 1440p@120hz with freesync/VRR and 55”.

Until you don't proof me this specific monitor (Xiaomi Mi Curved 34) enables 1440p@120hz with Xbox Series X, your comment is meaningless.

Yeah, there are some monitors with 1440p@120hz support for Xbox series s/x, that simply doesn't mean that ANY 1440p+ monitor with 120hz+ (especially 144hz+) can do it. Period.

I've tried everything, that (1440p@120hz) simply doesn't work with that monitor. I've already listed every step I've tried, I'm not gonna write it again.

Please read previous comments before posting the same dried comments...

I would look into your monitor and call DELL not Microsoft. I also have a One X and have never had any problems, as soon as select 120hz it automatically drops me down from 4K to 1440p. You must be misunderstanding something about your monitor as there
must be a defect of some sort or your monitor does not support 1440p at 120hz.

For reference, before responding I booted on both my One X's. One is connected to a Samsung 4K QLED and I had no problem switching from 4k 60 to 1440p 120. My other X is connected via an LG 4K monitor and again when selecting 1440p OR 120hz it automatically
selects 1440p or 120hz without any issues.

The Xbox Series X will do 120Hz but no more, regardless of resolution or monitor.

I would check to see if other Xbox Series X owners have confirmed to achieve 1440p120Hz on those monitors before purchasing.

Maybe a google of "xbox series x 1440p 120hz ___________ " and insert the monitor model to see if people have posted about their monitor and Series X working.