Someone disconnected Elizabeth (Parker) Clark from her 3rd husband (Nathaniel Andrews) saying that there was no proof of their marriage on 16 October 1721. However, Donald Lines Jacobus (in Families of Ancient New Haven, Vol. I) says that they did marry on that date. I could not find a marriage record online, but isn't Jacobus pretty reliable as a source? And as I state in the comments, they both lost their spouses earlier in 1721, so they were both available for another marriage. Here's a weblink to the Jacobus source:
By the way, the transcriptions of Wallingford Vital Records (from Barbour) show under Elizabeth Clark: "Elizabeth, m. Nathaniel ANDREWS, Oct. 16, 172[_ ], by Capt. Hall".