How to explain social prescription for gym unsuitable?

The rheumatologist requested GP do a social prescription for gym membership for fibromyalgia. The experience has been awful but I'm not sure how best to explain why I discontinued on the PIP form.

They told me the wrong time for the induction and then told me off for being late.
The staff member doing the induction was really moody, didn't show me where the classes took place or how to access them.
The gym classes that I might be able to manage (there aren't many) are always fully booked.
The walk from the car park to the gym is exhausting.
I'm struggling to manage basic daily living activities, I genuinely don't have the energy to do exercise.

Hi wootwoot, What an amazingly identical experience! I just wanted you to know you are not alone. Our 'wellness hub' [exercise machines that are great for me] opens booking by computer, only available if you have a membership anyway, at 6 am daily for the subsequent 7 days. My and my OH's health simply do not allow being up then and getting very stressed competing to book places online. Fibromyalgia as BIS says is a very sound reason [NOT an 'excuse'!] for finding this setup impossible. The GET 'Graded exercise therapy' programme was thoroughly discredited years ago but likely this hasn't filtered through to all the DWP and their contractors. It did our daughter with fm a lot of damage.
Best wishes,
Denby