Depending on where the Maverick was stored, it may have got some moisture build-up inside. This happened to me when I left mine in a patio storage chest last winter.
Try this.... remove the batteries of both units. Using a q-tip and some denatured alcohol, wipe all of the battery contacts clean. Then, with battery plates off, place both the transmitter and receiver a large bowl filled with white rice, ensuring both units are completely covered with rice. Cover the bowl with a towel and leave them there for 3-4 days. The rice draws the moisture from the units. Reassemble the units (new batteries), making sure there are no errant grains of rice left in either unit.
If that doesn't work, Amazon frequently has the Maverick's on sale. I bought a back-up set (ET-732) about four months ago for $39.