During lockdown some invoices may have been missed, or you might not have wanted to chase up an invoice because you weren’t sure someone would answer the phone. If you haven’t already begun chasing up late payments, now is when you need to be starting to push, and really drill down and understand why those invoices haven’t been paid.
Consider outsourcing the credit collection to an external specialist who is going to be chasing the clients at least weekly. Your number one priority now is to concentrate on growing your business, understanding the new environment. It might be that you outsource debt collection for 3-6 months or it might be that you outsource it permanently. Yes there is a cost, but the tradeoff is that it will reduce the likelihood of bad debts and should bring more cash into the business faster, and at the moment, everyone needs cash.