To expand on @nishu_kush's reply, you can install After Effects 24.x or 25.x without removing the version that you're currently working in (23.0). Just make sure that "Remove old versions" is disabled in Creative Cloud Desktop.
If importing the FLA into a 24.x or 25.x works as expected, you can then use File > Save As > Save a Copy as 23.x. The resulting After Effects project file will open in the older version of After Effects that you are working in.
If it turns out the FLA does not import as expected in a newer version of After Effects, then you'll want to patiently export SWFs from your FLA that can then be imported into After Effects directly. This is manually doing what the FLA Importer plug-in does when it's working as expected.