SQL Server database not able to update after restoration

We are migrating an application's database between servers and we have used the Attach method to attach the database files to the new location. After re-pointing the application to the new database all operations can be performed successfully except for one, which requires a group of tables modifications. These tables are linked with KFs and have an Index. It's strange because we don't face these issues with the old database. We have checked the Triggers, FK relations, and Indexes, and it all looks similar between both DBs. Is there a hidden relationship that requires fixing? P.S.: I am a programmer, not DBA and these are the steps I have performed: 1. Copy .mdf then paste to the new server 2. Attach the .mdf to the new 3. server Repoint the application to the new IP Test the operations, 4. it's all working and can insert/update the new DB A group of 5. operations related to logically related tables are not working.