Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services if someone:
Seek prompt medical advice if you are falling asleep during conversations, at work, or while driving, or if you have had a near-miss accident.
Do not drive when you feel unable to stay alert.
These are not typical routine sleep apnea symptoms and may indicate another urgent medical problem.
Arrange a routine appointment if you or someone close to you notices repeated breathing pauses, choking, loud snoring, or persistent daytime sleepiness.
You should also seek assessment for morning headaches, poor concentration, or sleep that remains unrefreshing despite enough time in bed.
The article also says
Contact your sleep service routinely if your mask is painful, your device is difficult to use, or symptoms return.
These problems often need practical adjustments rather than stopping treatment.
Every sign above is quoted from the sofidex article on Sleep apnea. If you are not sure, err upward — it is always reasonable to be checked.