There are 3 possibilities I can think of. I have seen all of these things happen at one time or another.
1. There are “hidden” characters in cell A1 that show as blank spaces but are actually special ascii codes. That is unlikely but I have seen that before.
2. There is a file permission issue and the OS is blocking SPA from reading the file.
3. There is a corrupted Photoshop preferences file which prevents the Plugins API from opening CSV files.
after you send me the file I will verify the file itself looks OK. If so, then it would have to possibility 2 or 3.
You can verify the file permission are set to read/write for all users.
Also, you can try resetting the Photoshop preferences and restarting Photoshop.