Not debiting my account then telling me im in arrears

I have been a member since 2019, debit orders going off every month. All of a sudden in August 2021 my debit order doesn't go off then September and October 2021 goes off then November and December 2021 doesn't go off. I receive an sms on the 9th of December 2021 only telling me that I am in arrears, when I phone them they can't explain to me why the debit orders didn't go through and yes there was money in my account every month. The debit order for August 2021 says no reject code, November and December 2021 says no authority to debit. I didn't even stop the debit orders at my bank or change my banking details! I haven't even been going to the gym because I didn't see the debit orders going through and wasn't sure what was happening with my membership, I even emailed them to find out.