I upgraded to a new iPhone 8plus from iPhone 6s. I cannot see my I cloud photos! What can I do???

Are you signed into Settings/Your Name/iCloud using the same Apple ID and is Photos syncing on?

Try Settings/Your Name/iCloud and slide off syncing. Wait a few minutes and then slide syncing on.

Last resort - have you tried signing out of iCloud and then sign back in?

what devices do you have and what are your iCloud settings on each device?

LN