Depends what kind of pelvic floor dysfunction. If the pelvic muscles are ‘too tight’, then it might be painful to insert as you won’t be able to relax the muscles.
If the muscles are ‘too loose’, it might not hold the cup inside as the pelvic muscles need to be strong enough to keep inside. With this said, it should be “safe” and is worth giving it a try. But a gynae visit is necessary to check which type of pelvic floor dysfunction you have. A physiotherapist can also help with strengthening pelvic floor.