Ok there has been some big update’s in Ver7. I would try this first:
Go to bench-repo folder
git pull origin
Go back to frappe-bench folder
Run bench update
If you are develop branch, you might be asked to run bench update --upgrade. This is because we have changed the version of frappe and erpnext in the develop branch to v7.0.0-beta
Make sure that ERPNext, Frappe and Bench are all on Developer Branch