Can you share screenshot of the model training with your output and expected output.
Please try these few methods.
first you can try deleting the cache and browser history. Log out from coursera and relogin to submit your model in case you are sure about your codes being correct.
If first point doesn’t resolve your issue, next you can try changing your system/computer to upload your model. note you will have to run the cell for the assignment and then download the model and then submit.
If all other do not resolve then kindly let us know. Your codes probably needs a review. You can refer the below link where learner had issue with the codes but had the expected output.
Also sharing a similar link
So kindly check if you have followed the steps I have mentioned to the learner in the tagged link.
If you have followed and still facing the issue, then one needs to review your codes and/or notebook.
After following the advice given by @Deepti_Prasad, I tried using incognito mode but it didn’t help. I then switched to a different browser (Edge) and was able to submit. Thank you to everyone who helped!