Probably should have given all that info in the beginning, sorry. The sync error is occurring on the Windows version (Windows 10 1803). When the problem was happening, I disconnected and had Enpass delete my sync file on dropbox. I do have my dropbox setup to use two-factor using a Yubikey on my PC. After reading the responses to this thread, I realized I had not tried the IOS version, yet, so I started up the new IOS version, it noted that I wasn't synced, so it setup the dropbox sync. No issues. I have a vault.enpassdbsync file now loaded in dropbox.