It takes too long to download my file on my device from icloud

Hi. I am using iCloud+ 2TB and my device, iPhoneXR which has plenty of gigas of storage so far.

Every single time I try to download My file from iCloud to my device it takes too long and doesn't even start to download. It just keeps loading and loading, never gets done.

I've been subscribing iCloud200GB for many years and been using this device for many months. Recently downloading any files from iCloud doesn't work. I'm not talking about huge video files, iCloud doesn't even work for downloading a 30kb-sized small pdf file!!

I upgraded iCloud 200GB to 2TB.

I have plenty of gigas in my device.

I didn't turn on the Low Data Mode nor Low Power Mode on my device.

My LTE works good. (I am writing this with my LTE.)

iCloud downloading fails even when I'm connected to a strong WiFi.

And Yes, I've restarted my device for several times.

It Just Doesn't Work.

I feel like I'm subscribing an iCloud plan and paying the fee for nothing.

Please let me know if there is any solution to fix this problem.