The phrase "not did" can be replaced by various other words or phrases to convey the same meaning depending upon the context of the sentence. The most common synonyms for "not did" include "did not," "was not able to," "failed to," "was unable to," "wasn't successful in," "didn't manage to," "couldn't," "didn't accomplish," "wasn't capable of," and "was unsuccessful in." It is vital to choose the appropriate synonym according to the situation to maintain clarity in communication. Using accurate synonyms can help in enhancing the quality of the message conveyed.