In order to relaunch or retry a migration that has ended in error, you must first go to the migration management of your SWPanel. To do this, from the blue side menu, click on Tools → for migrate websites → Manage migrations:
Next, locate the action of your migration and, using the [...] menu, click on Retry Migration:
You will have to accept the migration restart. To do this you must type the word that appears in bold in the text box:
If the migration fails again or even before relaunching it, it is advisable to check the error that caused it to fail the first time. To review the error, click on the menu [...] and click on View migration status.