The way to install older versions of Skyline is to go to the Unplugged Installer page:
https://skyline.ms/wiki/home/software/Skyline/page.view?name=install-64-disconnected

After you click on "I Agree" you can click the link which says "Archive" and download a .zip file containing older versions of Skyline.

If you send us your raw data files we can try to fix whatever bug is preventing Skyline from reading them.

You can zip up those files and upload them here:
https://skyline.ms/files.url
-- Nick

Whenever I try to download an older version of Skyline, I get the following error message: You cannot start application Skyline from this location because it is already installed from a different location. I am attaching the full error message. I have also uploaded two of the de-multiplexed files, the file names begin with nikkib5_062025. Do you also need the raw files before demultiplexing?

When you download the .zip file for the unplugged installer, you can just unzip it and run "Skyline.exe" from inside of the unzipped folders.
You do not need to run "setup.exe".
"Skyline.exe" will be in a folder under "Application Files".

Also, depending on exactly how you plan to unzip that file, you might need to "unblock" it first which I talk about here:
https://skyline.ms/announcements/home/support/thread.view?rowId=68468

I am able to reproduce your error in Skyline 25.1 with the files that you uploaded.
I can see what changed in the code which has caused this bug, and it has something to do with a parameter called "ignoreZeroIntensityPoints". (I am not an expert on this code so I will need to ask some coworkers exactly what is going on).

This bug looks like it will be straightforward to fix.
Hopefully we will be able to release an updated version of Skyline 25.1 which will fix this in a week or two.
-- Nick