If a candidate is allotted a seat in Round 3 of All India PG Counseling but does not join the allotted seat, their eligibility for further state counseling, including Andhra Pradesh state counseling, depends on specific rules set by the Andhra Pradesh counseling authority. Generally, if a candidate does not join after being allotted a seat in All India Counseling, they may forfeit their eligibility for state counseling in some cases. However, Andhra Pradesh may allow participation if the candidate hasn't joined any seat or hasn't submitted original documents.