OK, you say you only get 20 min's, does it record another 20 mins after that or do you have to restart the system to get it to record again?
Can you post your storage settings for "New"
I would suggest that you try to set the "Combine or cut video each: to some setting that works for you 12 or 24hrs and see if this fixes your problem, you may want shorter times if the individual files get really big!!
Here is what the help file says about that setting
The Combine or cut video option exists to combine events into fewer files when recording
when triggered, but it also cuts video into segments for the other recording modes. For when
triggered, un-check this option in order to have one file recorded for each event. Although
you may choose whether or not to create new files on a timed basis, you must always specify a
maximum size for a file before a new one is created.
If the cut time specified is 5 minutes or more and equally divides a day, such as 10, 20, or 30
minutes, or 1, 2, 3, 4, 6, 8, or 12 hours, recording will be aligned to the realtime clock. That
is, if you have a cut time of 12 hours, yet start recording at 11am, a new file will be created
at 12pm to cover 12pm-12am. The Blue Iris BVR file format allows for appending and
continuation across camera or software restarts, however, so this effect will be mitigated
when possible.