Tire is losing air but inner tube seems to hold air I got a flat on my back tire and bought a new innertube. I put it on my bike, filled it up but it lost all air again within minutes. I took the new tube out, pumped it up to find out where the hole is, but I couldn't find a hole and the tube didn't lose any air.
I installed the tube again and the tire went flat within minutes. I repeated this process a few times with the same result.
My bike is an E-Bike and I am reluctant to take it to a bike shop because in my area they charge some extra money for E-Bike repairs.
Just check the tube more carefully, some holes are very hard to spot. Put it into the water and look for bubbles. You must fill the tube and press it. Try hearing any hiss when pressing the tube in the air. There could still be a thorn in your tyre, we have many similar questions. It does not matter if it is an e-bike or not.