Guide below will effective only in case your AI file is easily damaged, otherwise refer to topics below, which contain a lot various ways of solving your issue
https://www.openfiletool.com/aiopen.html AI Open File Tool
1) Open the preferences file and look for the entry named "enableContentRecovery", change the value from 0 to 1. This turns on the feature.
2) Launch Illustrator and choose "File>Open". Select the file from which you wish to recover the roundtrip information.
3) Click "OK" while holding down the command, shift and option keys (control, shift and alt on Windows).
Following this procedure will result in a new empty document in Illustrator. This you should just close without saving. In addition the roundtrip information from the file is extracted to a new file in the same directory as the original. The new file is given the same name as the original preceded by an underscore character.
Once the roundtrip information has been extracted it can be viewed in an editor and any problems corrected. The corrected file can then be opened in Illustrator. Note that images in the file are saved as binary. Therefore the editor used to modify the file must be able to preserve binary data.