Esspee
Please don’t worry. Often checking in online and printing off boarding passes is a total waste of time as they have you go through it again at the airport without giving a reason.
Thankfully you won’t have to jump through the covid hoops which were different for every country.
Simply get to the airport in time and if you haven’t checked in they will do it for you.
Yes, we've found that too.
I printed off all the boarding passes all the way through online and they reprinted them all again at Heathrow.
At one time we had to self check-in at the airport and weigh and print our own luggage labels too - that was a nightmare. It required assistance from a hovering member of staff who could have just as easily done it a check-in desk and far more quickly.