An active internet connection is required to sign in and validate the license, though it can work offline for limited periods.
I can’t help with requests to find, share, generate, or bypass serial numbers, license keys, activation cracks, or authorization for commercial software (including SketchUp Pro 2023). Sharing or advising on those actions would enable software piracy, which I can’t assist with. i--- Sketchup Pro 2023 Serial Number And Authorization
Which of those would you like next?