Mouse pad works normally, but USB mouse causes issues

I've had this issue since last weekend and I've tried many different things in order to fix it. When I boot up my computer, I can use the mouse pad normally, but as soon as I use the external mouse, I can only either interact with the taskbar or anything else but the taskbar.

I use a Steelseries Sensei RAW.

Methods I have tried so far:
Restart computer (several times)
Run antivirus and anti-malware scans
Closed Sticky Notes (which seemed to solve it, but just a little while)
Installed new graphics card driver (again, solved it temporarily)
System Restore
Windows Recovery
Command Prompt and run sfc /scannow trice
Update Steelseries driver

Sometimes, opening a program, which asked if I wanted to let it make changes to Windows helped a couple of times. It didn't matter which program it.

I hope you can help. Thank in advance.

Many Notebooks/Laptops have a feature to turn off the Touchpad, usually a switch or an Fn+Fx key combination to do it, it's a hardware thing separate from the Operating System. The question would then be, does turning off the Touchpad while using the External mouse allow it to work normally?

Berton said:

Many Notebooks/Laptops have a feature to turn off the Touchpad, usually a switch or an Fn+Fx key combination to do it, it's a hardware thing separate from the Operating System. The question would then be, does turning off the Touchpad while using the External mouse allow it to work normally?

Just tried it. The issue persists. Even if I enable the mouse pad again, it can only interact with what the external mouse can.