Problem of downloading after migration


I migrated my website (Elgg 2.3.14) on a new server (PHP 7.0). The migration went well. Except that the "download" function doesn't work anymore for posts from the old server. For the new ones the "download" function is displayed and works correctly.

Here are examples for files and photos posted from the new server (everything works perfectly):
The file is downloadable:
The photo is downloadable:

Here are examples for photos and files posted from the old server (before the migration everything worked perfectly), the "download" function is not possible:
File not downloadable:
Photo not downloadable:

I tried to correct the error by:
- Changing the access rights 755 and 644 to 777.
- Deactivating the plugins and reactivating them one by one by seeing if the problem was solved after "Flush the caches" and "Upgrade".
But none of these solutions worked.

Maybe it is necessary to synchronize the database with a MySQL query? But I don't know about that and after searching on "discussion topics" i didn't find any answer. Do you have an idea or have you already encountered a similar problem? Thank you in advance for your answers.