External hard drive missing after update

Sorry to hear it. If you haven't already try a factory reset on the console to see if that helps. There's an option to keep installed games and apps so you won't need to redownload them and your saves are safe on the Cloud. You can read how to do a reset
via this link https://support.xbox.com/en-US/xbox-one/console/reset-console-to-factory-defaults

If that does not work the issue may lie with the drive itself and may need to be replaced. However, you could try the steps listed below to reformat the drive and then re-attach it to your Xbox. Please be aware that these steps will result in all games
and apps being deleted from the drive. Your saves will still be safe.

If you need to reformat your external hard drive on the PC please follow the steps below to have the PC recognize the drive.

1. On the PC go to the Start Menu and type Disk Management in the search bar then press enter. If any pop up come up just click Cancel

2. Search for the drive on the list. It should have a red arrow next to it and say that it's not initialized

3. Select Initialize in the pop up menu. Don't change any info on the next menu

4. Right click on the drive and select New Simple Volume

5. Click next on all screens until you see Finish. Click it

From here you should have a notification that you've connected a new hard drive. You can now find it in the PC folder, right click on it and select Format. I would recommend unchecking the option for the fast format and let it do a full one.

You can read the article on how to do the reset via this link
https://www.gottabemobile.com/how-to-fix-your-hard-drive-after-using-it-for-xbox-one/

One final note. If you do not see an option to Initialize the disc right click on the drive and select Convert to MBR. Others have luck in selecting this option to have the disc be read by the console without reformatting it.

Try plugging your hard drive into your PC to make sure it is recognized on there as well. If not, then download the hard drive tools from the manufacturer website to check to see if the hard drive has any issues which the tools may be able to fix.

Could be the external hard drive causing the issue then it won't be the first time I seen errors appearing after updates on external hard drives. Try installing it on internal drive instead if you can?.

seems to a lot of problems with external hard drives after the recent update

Hard reset, remove/add external hard drive, hard reset again.

Are the missing games on the external or internal storage?