We need a bit more information in order to effectively support you - can you please include the output that you see when you get the error? Either re-run the command with the --verbose flag, or copy-and-paste the error log file.
Also - are you seeing the same error in each version of QIIME 2, or different errors?
This one seems to indicate your table is not a "real" .qza. I'm not sure whether it's possible for that to pop up if you have a bad filepath, but that's where I'd start. Please make 110% sure you've correctly spelled that very long file path. If that doesn't fix the error message, please share the details on how you made that FeatureTable and we can look into it further.
Only usable "Choices" should show up in the command-specific documentation or when accessing help through the command line interface, but it's totally possible we overlooked something in the tutorials. I wasn't able to find any uses of observed_otus in the tutorial source code, but if you have an error in mind, I'd love to fix it. Please let me know where you encountered the issue.
If you can, please share the FeatureTable you believe to be faulty and the exact commands you are trying to run. I'll try to reproduce on my end and we can go from there.