Windows 10 has always had some periodic amnesia with the tray icons, as per location and shown/hidden state; here is the fix for the problem (this will retain tray icon shown/hidden state and position between reboots).
This fix is only for Windows 10 (tested in Windows 10); Windows 11 may or may not store the tray icon data in said registry folder.

1) Export the following Registry folder to TrayNotify.reg
HKEY_CURRENT_USER\SOFTWARE\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\TrayNotify

2) Using Task Scheduler; create a task
a) General: Run the task using the User account that has administrator privileges ; Run only when the user is logged on; Run with highest privileges; Hidden; Configure for Windows 10
b) Triggers: At log on; At log on of any user (you can set this to the particular user or leave as is).
c) Actions: Start a program; regedit /s "{path to TrayNotify.reg}"
d) Conditions: deselect everything
e) Settings: Allow task to be run on demand; Run task as soon as possible... ; If the running task does not end... ; do not start a new instance


That is all. I only have one user account on my system so this automatically loads (when loggin in) the data into the registry and the tray icons are perfectly restored as when I saved the registry entry.

Enjoy!