Robot Vacuum Woes

I was excited to get my ROBOT VACUUM. Set it up no problem. Updated firmware. Great!
Ran it the first night and it mapped the entire space perfectly and went to sleep in it’s charging port. I know that it had to recharge at least once to finish the job.

But for the last 2 nights, “SARGE” doesn’t finish its job and I find him in the middle of the floor with what I believe is a dead battery. The APP says that the robot is disconnected from the internet, which would make sense if the battery is dead, but why didn’t he go back to base to recharge? I know he did it before.

BTW, I found the charger NOT where I placed it last night, so I used some adhesive tape to hold it in place when the robot returns and leaves. Before you say that this was my issue, this was NOT the case the night before. I don’t believe the charger moved 2 nights ago, and the same thing happened.

I appreciate any help/insights I can get…