Can I force iCloud photo sync on a device

I haven't used Windows in years, and I'm not exactly sure what you're asking. Have you uploaded a picture from your computer to iCloud Photos, and you want to see it on your phone, requiring syncing?

Syncing is a background operation, and people don't like their web surfing to be slowed by it, and they don't want their batteries to run dry from it. Because of this, background operations like syncing are suppressed while the phone is on battery or being used. So the best way to get syncing on the phone is to plug it in (maybe better with a cable,) have good internet, and leave it alone.

Sometimes, though, I try doing a forced re-start:

Force restart iPhone - Apple Support

Not which I’ve encountered. (Hopefully others in this community might know of one 🤞)

Being connected to a solid, high-speed WiFi or 5G connection is likely the key determinant.

I do sometimes click “Backup Now” to initiate an iCloud backup.

(Although I suspect it makes absolutely no difference, it DOES make me feel like I’m contributing.)