While most transactions will earn you Grover Cash, there are some exceptions:
Card transactions below €1
Mail order or phone order transactions
Declined or expired reservations
Payments to gambling companies
Money transfers to banks
For more details, check out the full list of excluded transactions.
You can earn a maximum of €60 per month in Grover Cash. Once you reach the €60 limit, you'll have to wait until the following month to restart earning Grover Cash.