Bathtub (no shower) has single handle faucet which provides plenty of cold water however zero hot water. Instead there is a trickle of cold water. Just starting to research this so I haven't done anything other than check the manifold shutoff valve to make sure the hot water one is in the "on" position. Thanks so much!

Possibly plugged hot port in the cartridge. Shut off the water, pull the cartridge, clean the ports in it, flush the manifold, reinstall the cartridge.

Yep agree with ma0641 but Please tell us the brand and the model number of your faucet that we further assist you, Thanks.

John