I just scanned the thread so sorry if I missed this but have you checked the drives "smart" reading? Even if drive doesn't show in this pc it should show with smart check. basic hard drive health test. download the zip version. it's portable so you don't even install. just unzip and check
https://crystalmark.info/en/download/#CrystalDiskInfoif it shows any "caution" or worse the drive is failing. Note that if it is failing and not just the enclosure I would stop all attempts yourself!
The tech you took it to should have removed the drive to scan it. pulling a drive from an enclosure is easy (unless it's a my passport type).
The guy I went to was a joke. Worse than Best Buy. All he did was run a couple recuva type scans.
I do computer repair for a living. I know my limit on data recovery as do most techs. Hopefully he did more than recuva but unless it's a clean room situation then software based is all most local guys will attempt.
I have heard very mixed results about the 300datarecovery place. I have sent work here with good results.
https://www.recoveryforce.com/pricing/