Insufficient space error on iCloud despite available storage

Hello, I have a 2TB plan, of which I'm currently using 160GB, and have 1.84TB of free space available, yet every time I try to backup files from my windows based laptop, I keep getting messages saying there is insuficient space and that, i.e., an additional 39.6GB are required to copy the files, and can't copy my files, and, again, I have 1.84TBs of free space!!! This is so frustrating, I haven't been able to find why this is happening, I will appreciate very much to anyone who can help me fix this issue.

[Re-Titled by Moderator]

Original Title: Insuficient space?!?!?!?!