Both .rar and .rar5 files are archives, just in different version of WinRAR. There was a time when WinRAR experimented with new algorthm and changed extension to rar5 for that version, but it went back and it's just RAR now. You can repack archives with WinRAR and if you use the latest version of the tool, you will get files compressed with the latest algorithm. No rar to rar5 conversion is most likely required.
Updated: October 9, 2023