Make sure nothing is obstructing the charging port on either the mug or the coaster. Check that the included power adapter isn’t frayed or damaged in any way. Gently clean the coaster and see if it is damaged or visibly malfunctioning in some way. When placing the mug on the coaster, align the metal rings on the mug with the copper rings on the coaster, and be sure that the rings look and function as expected. Do not attempt to use the charging coaster if its copper rings do not look right, or if they appear damaged to any extent.  You can also try plugging the power adapter into a different AC wall outlet and see if that helps. Alternatively, try using a different power adapter when attempting to plug in the charging coaster. Never attempt to disassemble or modify the charging coaster on your own. If all else fails, feel free to reach out to our Customer Support team for further advice.