If you put a fresh set to two AAA cells in your mysterious thingy and leave it turned on, does it work? How long do the two AAA cells last before it no longer works?
You have probably blown an internal fuse in your multimeter. Get a new fuse or a new multimeter and learn that you never try to measure using the current function of the multimeter by placing the probes across a voltage source, even something as "low" as a pair of series-connected AAA cells. You have to open the circuit between the cells and the load by removing one wire (cut it if necessary) and placing the probes between the wire end and point you removed the wire from. If the meter has a 20 A functions, this will invariably be on a separate meter jack. The mA and μA current measuring functions will share the same jack as the voltage and resistance measuring functions. In all cases you will use the COMmon jack as the second terminal. It is unlikely that you will have blown a fuse using the 20 A jack, but it is also likely you won't see much current there from two AAA cells wired in series. So try the mA range first. Find a low-valued resistor, say, 100 to 1000 ohms and connect this resistor in series with one AAA cell and your meter test leads. Report back here what current you read. This to verify that you are measuring current properly. If the multimeter has AC versus DC selections, make sure it is set to measure DC current. Do not omit the resistor when making current measurements. Do not place the probes directly across the AAA cell terminals while trying to measure current.
Better get those stalls finished before Global Warming kicks in for your area. Ugh! I did that one summer for four horse stalls. There's gotta be a better way... but it sure made for some really green grass that year.