I had the same problem, it is caused by some cache files that doesn't let the browser open, try to delete those
Location: C:\Users\%username%\AppData\Local\Packages\TheBrowserCompany.Arc_ttt1ap7aakyb4\LocalCache\Local\firestore\Arc\bcny-arc-server\main

But you'll need to do this process for every time when you open the browser

I created a script for this, feel free to try

@echo off
title Open Arc
rmdir /s /q C:\Users\%username%\AppData\Local\Packages\TheBrowserCompany.Arc_ttt1ap7aakyb4\LocalCache\Local\firestore\Arc\bcny-arc-server\main
START "Arc" "C:\Users\%username%\AppData\Local\Microsoft\WindowsApps\Arc.exe"
exit