Can't update (nor restore) iOS on Catalina

So your doing this through the new way in finder? if so, maybe perhaps re download it, and see if that works.

Once the device shows in Finder you will need to hold option + update/restore to select the ipsw

Since your iPhone is a test device as betas are not intended for normal use devices then wipe the phone back to scratch to install and test the new iOS.

It does seem like there is a long delay, but then the process starts. once selected the file ipsw file it took a good 10 or more minutes of doing nothing, then switching to "preparing to install", and then another long delay before asking for passcode to start the process.

Same problem here. Also Music and appleTV crash after 5 seconds.

when i hold option and the Restore Ipone button nothing happesn?

Hi carlosfromhouston, Make sure that if you have Configurator installed that it is not open. Make sure you’ve signed out of find my iPhone as others have mentioned. Plug your iPhone in, and then wait for it to appear in finder. Option (Alt) + Click on Restore, and wait for it to open the window for you to point to your download. It may take a couple of minutes to open the window, it can be a little slow to respond. After you have managed to select a file, it will warn you it will erase and restore the device, and verify with apple (make sure your iPhone UDID is added to devices lost in your developer account) - it will then restore 13 to your device. Be patient it does take a little while and for the whole time it will display “MAC is preparing to restore your phone” there won’t be a progress bar on your Mac. The phone will have a progress bar. It will fill once, then restart, before filling again, and then restarting the final time (at this point Finder will tell you your device has been restored, and will appear once it has rebooted).