There's no problem with your APFS formatted hard disk drive and USB stick.
Since you formatted both of them to APFS (Encrypted), in simple words, the APFS drive is encrypted and protected by a password you've set. Every time when you connect the encrypted APFS drive to your Mac, macOS will show a popup window to ask for the password to unlock the encrypted drive before mounting it.
I think that you probably ignore the pop-up warning so that the drives are visible but in the unmounted state in Disk Utility. If you want the APFS-encrypted HD and USB flash drive can automatically mount every time you connect it to your Mac, you can:
- Eject the two drives.
- Reconnect them to your Mac.
- When the alerting dialogue box shows up, tick "Remember this password in my keychain".
Once the password of the encrypted APFS drive is stored in Keychain Access, the external hard drive won't ask for password on your Mac the next time.
It worth mentioning that APFS and APFS (Encrypted) are different. APFS (no encryption) formatted drives can auto-mount on Mac machines without unlocking.
