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 for dizziness accompanied by new facial drooping, one-sided weakness, difficulty speaking, severe trouble walking, fainting, chest pain, a sudden severe headache, or loss of vision.
These are not typical effects of the Epley maneuver or uncomplicated BPPV.
Seek prompt medical advice if you develop persistent vomiting, cannot keep fluids down, have new hearing loss, or develop significant neck or back pain after the procedure.
Contact your healthcare team during routine hours if positional vertigo continues after treatment, returns later, or is affecting walking, work, or sleep.
You may need repeat testing or another maneuver.
Every sign above is quoted from the sofidex article on Epley maneuver. If you are not sure, err upward — it is always reasonable to be checked.