Welcome.
I don't use any of the Model series mixers, but the first thing to consider would be incorrect "Mark" settings.
That's addressed in Section 8 of your owner manual, so no need to repeat it here.
Let us know if that fixed the issue so others can benefit in the future.
If that doesn't correct the issue, then you'll need to be much more precise for trouble shooting purposes, starting by confirming the firmware is up to date and that you're using a TASCAM tested/approved SD card.
For us to help going forward, you'll need to describe in detail each of the steps and settings you've followed for both "Record" and "Playback".
That will save all of us time by avoiding incorrect assumptions; by avoiding the need to ask for additional clarifications from you; and by avoiding unproductive guesswork.
As a new member of this site, you may find the Stickies section of this forum to be a good resource.