Bathroom sink leaking from water supply connection to faucet

[losten]

Hello, all. I recently discovered that my bathroom sink was leaking where the cold water supply line connects to the underside of the faucet. I initially tried tightening the connection but that didn’t help. I replaced the water supply line but I am still having the same issue with it leaking at the connection point. And yes, I made sure to tighten it according to directions.
At this point I’m worried that the issue is with the threads on the faucet itself and that I’ll need to replace the entire thing. Is there any other solution that could fix this leak without having to replace the faucet?
(The pictured water supply line is the one that was replaced. The new line is a compression braided stainless steel supply line.)

 

[Weekend Handyman]

I am not a plumber or a pro. It should not be the threads. I am pretty sure the face of the faucet connection pressing up against the washer in the supply line is what creates the seal. A few things I would check: 1) Is any of the old washer stuck to the face of the faucet connection and not letting the gasket seat correctly? 2) Are there any dents our gouges in the face of the faucet connection that are creating path for a leak? 3) Is the washer present in the new supply line (could have fallen out at the bin in the store)?

 

[Sponsor]

 

[James Henry]

If you put it on hand tight and then turned it 1/4 turn, just keep tightening it until it stops leaking. You won't break it.

 

[Reach4]

A tiny bit of Silicone Faucet Grease on the seal and on the threads will help. The stuff on the threads lets you turn more easily. As James says, that is not easy access, and you cannot come near breaking it.

0.5 ounce tube may be a lifetime supply.