cant upgrade my macpro early 2015 frim mojave to Montery... any solutions please...

The MacBook Pro 13” early 2015 tops out at macOS 12 Monterey.

An upgrade from macOS 10.14 to macOS 12 is supported.

What is the error or symptom you are encountering, and what have you tried?

Any add-on VPN apps, add-in security apps, add-on cleaners, or similar, installed?

PS: “Mac Pro” and “MacBook Pro” are very different Macs. There is no Mac Pro (desktop) model from 2015, though there is a MacBook Pro (laptop) model from early 2015.

If you have already been in contact with Apple, best re-contact them.

Causes here can involve local networking errors, problems with the Mac itself, local resource errors that can be cleared by a reboot, problems with add-on apps including add-on VPN apps and add-on security apps, with the Wi-Fi or wired network connection, with the Wi-Fi router, and with the ISP link. Problems with the Apple servers in your country or region, too.

If you want to pursue this here, download and run EtreCheck, and share the report to the clipboard. Then open a new reply here, and press the Additional Text button that looks like a printed page to get a text input box big enough to paste the hardware and software configuration report here, and paste and post that report here.