The specific release(s) of MATLAB you can install/use depend on the specifics of your MATLAB license. You should check with the administrator of your MATLAB license for specific details about what releases are supported.
Assuming your license is valid for MATLAB R2024b, you can download MATLAB R2024b from the MathWorks website (if you don't still have it installed) and you should still be able to activate and use MATLAB R2024b as long as your license remains valid.
If you need to get the installer again, the default selection on the MathWorks website will be MATLAB R2025a, but R2024b is still available. For example, when I go to the download page, this is what I see:
You can select what release to download by changing the drop-down menu in the corner.
That being said, please report any performance issues you have with MATLAB R2025a to MathWorks so we can investigate and resolve those issues. If you can provide specific reproduction steps to reproduce the slower performance, you can report that to MathWorks technical support, or you can post a separate question to MATLAB Answers with detailed reproduction steps and members of the community may be able to help you optimize your script to perform better in MATLAB R2025a (and possibly even better in R2024b).
