Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency help for thoughts or plans of self-harm.
Sudden loss of calculation ability also needs emergency assessment when it occurs with confusion, facial drooping, weakness, severe headache, trouble speaking, a seizure, or a recent head injury.
That pattern is not typical of developmental mathematics disorder.
Seek urgent mental health support if distress about school or mathematics leads to severe withdrawal, refusal to eat or attend school, or talk of hopelessness.
Arrange a routine assessment when mathematics difficulties are persistent, significantly greater than expected, or affecting education, work, confidence, or daily tasks.
A child does not need to fail repeatedly before concerns are discussed with the school and a healthcare professional.
Routine help is also appropriate if there are signs of ADHD, language difficulty, hearing or vision problems, anxiety, depression, or another condition that may be affecting learning.
Every sign above is quoted from the sofidex article on Mathematics disorder. If you are not sure, err upward — it is always reasonable to be checked.