Yah very likely the latter, problem between receiver and FC regarding the not seeing values in the receiver tab of BF configurator. Hooking up receivers is notoriously difficult, it can go smoothly but is one of those places nearly everyone gets hung up at some point because of some misconfiguration, the stars need to align for everything to work with regard to the receiver input.
For the motors you should be able to bench test them with the props off and using the motors tab of betaflight, there is a toggle you have to "check" to on mode that warns you to remove props (please for the love of all that's holy take the props off before bench testing, anything above 2" blades can cut you up pretty bad). Using the motors tab with a battery hooked up to the quad you should be able to send control signals from the FC to ESCs to get the motors spinning. Also on first plugging in the battery you should hear ba-da-ba, then a pause then beep-boop, if you hear the ba-da-ba but no beep boop it means the ESCs to motors are good or else won't hear anything and battery power is getting to ESCs, the last two tones, beep-boop come when the ESC gets a 0 throttle signal in from the FC which should happen basically immediately, if it doesn't then there is an issue with the connection between FC and ESCs, if you hear no ba-da-ba at the beginning then problem with motors hooked up to ESCs or problem with battery power getting to them (a ESC+Battery+motor is enough to test out the ba-da-ba, first three startup tones sound).
Regarding the receiver would try and diagnose/fix that issue separately. There's a small checklist of things that need to be correct for receiver data to come into the receiver tab:
1. TX must be bound to receiver, if not you will likely just see idle values being sent from the receiver in receiver tab which will appear similar to no data at all (unless showing RSSI which will bounce around).
2. In BF ports tab make sure the Serial RX toggle is on for whichever UART your receiver is hooked up to (as far as I know no harm in guessing if it isn't clear which one it's hooked up to)
3. In BF configuration tab the "Receiver Protocol" drop down needs to have the correct "wire protocol" for how the receiver is sending data over the serial line specified in ports tab in step 2 here.
If all three above are correct you should at least see sliders moving around in the receiver tab, if they are the wrong ones you'll have to change the channel mapping on the receiver tab, common combos are AETR (aileron elevator throttle rudder), or TAER, again you can just swap letters until the right sticks control the right thing but can usually see like yaw and roll are swapped then swap the A and R. One last thing once receiver is sending data into that tab is to make sure the value shows 1000 when stick at minimum and 2000 when stick at maximum, if the values differ you can easily remap using the CLI tab and rxrange command.
