If the Project Code is not showing in Project Management after creation; it may be a simple issue with the security permissions, which is covered in the article about the project list does not return expected results.
Otherwise, if you are not able to view the Project in either Project Commencement or Project Management and it also doesn't exist in Dimensions, Support will need to run some scripts on the database. Therefore please raise a new case online and reference the title of this article and please supply the Project Code or other specific information about the new, missing, Project Code.