My letters are not uploading into LG Pass. The first 20 did but I tried to load more and they didn't. When I drilled down, the offer date is 1969

You have it set to drip 20 offers per day. That means as you upload them they will go into a queue and we will mail 20 more at 4am each day.

The 1969 date gets replaced when we upload them to lob.