Chartman,
Sorry I'm a bit late getting back, I've been out today. I had loads of problems yesterday, and some the day before. I got no backfill of any data files for data from the 31st on the 1st April, or for the 1st on the 2nd. I tried deleting the ends of files from Sierra and letting it reload, but it only filled current day's data each day.
In the end I got someone at MT who said they had a problem with one of their servers, which I was on apparently. Logged of and on, no change. Told him which server, "Ah, it wasn't just one server, that ones bad too!". Finally I hit a good one, deleted 2 days data from the end of each file (position the last point you want at the right hand end of the screen, right click, select Edit Minute Data, and Delete to End of File) then Sierra does the rest, provided the data source is good.
There's a note on the Sierra site about version 36 (the next one) apparently that will help deal with this, it will reload the last 2 days data automatically even if some is there already.