My answer, if you read it, is to check your volume on the tape deck. It should be less than 75% but more than 25% in volume's loudness. Too loud, and the Apple will ignore it and give you an error. Too soft and it will not be heard and the Apple will give you an error.
What I did not mention or should have asked, what type of cassette drive are you using- Mono or Stereo? If it is stereo, you tie tie the left and right audio signal into a mono signal with a Y-Cable. Computers those days used mono tape decks.
If you are brave (or stupid, depending on the point of view), play back the tape on an audio deck at 10% to 25% volume and listen to the buzzing binary sound. If there is a drop out on the sound any place in the file track, then the file will not load.
Sheesh.... Atari kept it simple, its file transfers from tape can be heard on while loading on the unit, and it loaded it in blocks of 256-byte blocks. So it would load, pause, load, pause to the last block which was usually Zero'd out and make a constant Zero End Block tone. Only an 8-bit Atarian would know that, however. Commodore files, when played through a tape deck were double saved - for part was the file it self, the second was a copy of it, which verified the first part. If there was a difference between the two file parts, it would error out with that infamous "Load Error." message!