"WorkSafe is continuing to engage with this business to ensure they understand and meet their requirements under the Covid-19 Protection Framework," he said.
The gym declined to comment. Its latest social media post on Sunday, coming after New Zealand's move red light, said it was limiting classes to 25 participants and only critical support people could accompany students to class.
New Plymouth MMA is not the only gym to run into issues with the use of vaccine passes.
West Auckland gym Oliver MMA HQ has been fined $36,000 to date for intentionally allowing unvaccinated staff to work and staying open without checking gym users' vaccine passes - what WorkSafe calls "egregious breaches" of Covid-19 rules.
The New Lynn gym remains open on its current premises and has no plans to move out despite an offer from their landlord to wipe its rental arrears of some $160,000, gym owner Steve Oliver told the Herald.
Under the red light setting, gyms and indoor recreation facilities cannot open if they do not follow vaccine pass requirements.
Businesses that do can have up to 100 vaccinated people based on one-metre distancing in a single defined space at any time.
Industry association Exercise NZ says the majority of New Zealand's estimated 1500 gyms and exercise studios are on board and checking vaccine passes.
"There are just individuals who, I'll put it nicely, just don't get it," said chief executive Richard Beddie.
"The key protocols for gyms and indoor exercise facilities at red are: compulsory use of vaccine passes for staff and members, limits on capacity, and thorough sanitation practices.
"But I much prefer when people are being up front about it," he said, urging businesses that choose not to follow the rules to inform people so they can make informed decisions.
"The danger is when people are not following the rules and not telling people, in other words they're letting unvaccinated people in."
