This type of adapter is used to plug into a 15A outlet on a small generator. The reason your Microwave or AC unit is not running properly is due to not having enough wattage available from the generator you are connecting to. If you were to calculate the maximum wattage you could run through this outlet/adapter it would come to (Amps-15 x Volts-120 = Watts-1800). Most microwaves could require more wattage at start up which means it would not operate properly and all AC units require more watts to get the compressor motors started. It is best to calculate your wattage needs by looking at the starting amps of the items and then do the same calculations to find out the wattage needed and you can size the generator from there.
Remember this outlet is designed for 15A not 30A and you would need a different adapter or cord to get higher wattage for your appliances.
RV Power Cords