Just for anyone that stumbles across this. I was actually just having the same issue, and I was using a Linux desktop with ubports-installer, and I still was getting the same exact issue as you. I did however do as Keneda suggested, and installed Android 11 (previously had Android 13). I ran ubports-installer again, and the installation worked perfectly after that.
You can find an installation for Android 11 in the link below.
https://support.fairphone.com/hc/en-us/articles/18896094650513-Installing-Fairphone-OS-Manually
Good news is that it's actually very easy to reinstall Android 11. Your bootloader is probably already unlocked, so I think all there is to do is just download the right Android version that they give, and run the right script. I would do the Android setup on a Linux desktop though. It makes it a lot easier; rather than worrying about USB drivers and stuff.
Good luck!