DM6500 Current Measurement

Not able to measure current using DM6500 in both front and rear terminals. Fuses for both channels are OK. What else needs to checked? The device was working fine and we were able to measure the current. In between something went wrong and suddenly it stopped working. 

Do you have a second amperemeter?

If yes, please do a series connection with both systems to measure the current and compare the results.