Reading between the lines would leave me to believe that they are not communicating their expectation to you effectively which leaves you confused.

I think 1 or all of these things are going on:

1. They do not approve of the work that you have done and do not want to directly confront you about it. Maybe they even have tried to confront you, but then you just point back to your code that you think is okay but is not really ok in their eyes.
2. They do not believe the other department is holding you back. That is a common excuse I see used all too often and immediately raises red flags to me...
3. They have been too busy to take the time to look at your work in detail and your presentation was not effective at communicating what you have accomplished.

In the future, and, even right now, you can schedule check in meetings as major milestones are completed and send status updates as you make progress. You can also try to be humble and practice active listening to really try to understand what your bosses are trying to communicate to you. Rephrasing what they are asking you to do in the form of a question goes a long way.

Unfortunately, I have been guilty of this in the past too. Very often it is easier to just redo code rather than confronting a temporary employee that is way off base. Sometimes, I can tell based on politely, indirectly confronting them that they will become very defensive and feel insulted if I go into detail about why the code is not so great. For example, I had someone redo a ML library from scratch after I had given them a link to the library. It was not worth my time to try to correct them, since I saw they were too stubborn to use a 3rd party lib and wanted to do things their own way. Something that could have taken a day lasted months for no reason other than stubborness.

Not trying to pin this all on you though. It is really unfortunate that your boss did not atleast take a peek at your commits and comment on some of them. Many modern shops require continuous peer review in the form of pull requests. That can of environment probably would of helped you thrive alot more.

Anyway, I would not give up yet. See if he has a little time to sit down and walk through all the features with you.

Just tell him that you want to polish things off and are trying to make sure you incorporated everything that he wanted. Go in with active ears though, and try your best to not correct him. The goal is to learn what he feels is not complete. Notice that what he feels may not align with reality, but it is the most valuable piece of information that you are completely missing right now.

Good luck!