Hi @busher,
Please firstly check you have enough permission to create an item in that list. Then, give a try to reindex the columns in the list if this issue persists.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.