Exception:
“We couldn’t find the record you’re trying to access. It may have been deleted by another user, or there may have been a system error. Ask your administrator for help.”
If you face the above exception, check the following
1. Check whether the Lightning Record page has any Standard Related Component(Parent record) added to it. If yes, check whether the user has access to the parent record.
2. Sometimes, this is caused by the global actions being assigned the default or placeholder –Master– record type.
3. If it is on Activity Timeline, check https://help.salesforce.com/s/articleView?id=000350552&type=1.