Wax Ivy does need to have moist soil and loves bright light, though will tolerate a lower light condition.
Inspect the leaves, indoor plants can be susceptible to some insects,
If you think it may have been overwatered it could also be root rot.
Is the plant root bound? Maybe it needs repotting in a slightly larger size pot, no more then 1 " larger with fresh good quality potting mix would help if the plant is root bound.