My log spans several decades. Starting with the most recent entries, I have been uploading to LotW using DXKeeper. Working back in time, I got to June 2014 and found I could not upload to LotW. It turns out that log entries from Februrary 2012 through June 2014 have their Online QSL tab's LotW "sent" field set to empty. All other QSOs in my log that have not been uploaded to LotW have that field set to "R".
I do not know why the "sent" field is empty for that block of about 24,000 QSOs. I checked some backups and found it that way since 2018, my oldest backup.
Am I correct in thinking the "sent" field needs to be set to "R" in order to upload these QSOs to LotW? If so, how can I do that?