Try these first
- Refresh the page, and open it once in a different browser.
- If a photo will not upload, check the file size; very large images are rejected.
- On a phone, switch from mobile data to Wi-Fi (or the other way round) and try again.
If it still will not work
Open a support request and tell us: which screen you were on, what you were trying to do, and the exact wording of the message on the screen.
Attaching a screenshot turns a day into a few minutes — “it gives an error” on its own tells us nothing, an image tells us everything.