Short answer: Most likely the policy’s definition of disability changed. Many group LTD policies pay while the person cannot do their own occupation for an initial period, often 24 months, and after that only if they cannot do any occupation they are reasonably suited for.
Own occupation means the employee is disabled if unable to perform the material duties of their own job. Any occupation means disabled only if unable to perform any job they are reasonably suited for by education, training or experience, usually with an earnings test. Group LTD contracts commonly use own occupation for the first 24 months of a claim and any occupation after that, which is why a claim can end at the switch even though the condition has not changed.
Read the definition before comparing prices. A longer own-occupation period, or a true own-occupation policy for specialized professionals, costs more but is often the whole value of the coverage for a surgeon or other specialist.
The any-occupation test is still usually looser than Social Security’s, which asks whether the person can do any substantial gainful work that exists in the national economy (42 U.S.C. 423(d)(2)). The exact wording, and any earnings threshold, is in each contract.