Parking Restrictions after 8 years

I am currently the President of a Master HOA. Within the master is a sub association that has become non functioning. Written in the Master documents is that everyone, including subs must abide by the governing documents, one of which is overnight street parking.

The Master left enforcement of our covenants to the sub in those areas until now due to it being non-functioning. The concern is that we have not "enforced" no overnight parking for 8 years and based on a board vote, chose to resume.

This has obviously caused many issues, some of the HOs within the sub only have single car garages. While clearly documented and filed with the state, can we resume the parking enforcement? I know variances will get many in trouble but struggling on feeling right with starting enforcement after 8 years of not.

Been doing this for 36 years, so here's the rub on that issue:
The master HOA may be able to enforce the sub's C&R's if the master documents say so. Otherwise the Master needs to first appoint temporary board members for the sub to do it legally.
Next be a neighbor first and be understanding, as you seem to be. Send out the notice. Enforce with fines first, not towing.
Give them a chance and a set amount of days, say 30 days, to fix the problem. This will 1- give them the chance to fix it, 2- it will gain you support and cooperation, and 3- it will reduce the uproar.
Put the fines in the sub's reserves.build it up, this will be more attractive in getting a volunteer to step up and volunteer.