I was adding more panels to my existing array the panel voltage is 43v and i have a total of 4 panels. While connecting the MC4 connectors there was a pop sound and some burnt smell came from the mppt. The voltage registers on the app but it only charges 1 - 2 watts. No error is displayed on the application. Is there a fuse which might have blown? is there a way to reset?
Did you connect the panels in Series? So, a total of ~ 170V?
Normally there is a check on PV Voltage and the mppt would refuse to operate if exceeded. However the manual also states a absolut maximum that should not be exceeded - and that’s not 70% above rating. 
Fuses blow due to excess current, not due to excess voltage, so I assume the smell wasn’t a internal fuse.
Get a new one, put that on your “don’t repeat”-list.
There is a fuse inside, but you have to destroy the cover in order to change it - so this is not a user serviceable item. This fuse normally only blows if you short the PV output while the battery is connected. 1-2W indicates internal consumption.