If you are trying to migrate the entire site, make sure when migrating the site, you have selected everything(database + files).

If you are sure that you have included everything when performing the migration, then you can check the following possible causes and solutions to this issue:

1. Restore was not completed successfully

Please make sure that the restore was completed successfully. Did you see the success message after the restoration? If you did not see the message, please run the restoration again and wait for the success message to pop up, then check the website again.

2. The target site is not a fresh WordPress installation

Please set a fresh WordPress installation on the target site then upload and restore the backup again.

3. PHP environments are different 

Please make sure that the source site and the target site have the same or similar PHP environment.

4. Cache, firewall, 301 redirect plugins

Please temporarily deactivate cache plugins and firewall plugins on the source site, then run migration again.

5. Using Elementor and Oxygen page builders

Some themes or page builders (for example, Elementor and Oxygen) have their own migration methods, once the migration is complete, their data need to be regenerated.

Migrate Elementor: Go to WordPress admin dashboard >> Elementor >> Tools >> General >>  Regenerate CSS and click on Regenerate Files button and save changes.

Migrate Oxygen: Please follow the instructions in their Importing & Exporting documentation.

6.This can be a database service problem

In this case, please go to WPvivid settings > Advanced settings > Choose PDO in Database Access Method > Save Changes, then try to perform the migration again.