When working remotely, network connections are not as stable as on campus, so it’s possible that shares/drives (H:\) disappear.
You can connect (“mount”) the drive easily:
1) Be connected via VPN (H:\ S:\ and other drives won’t work without VPN!)
2) Open the Windows Explorer
3) Right-click on “This PC” (“Dieser PC” if you use German Windows), and select Map network drive…

4) Select the “Drive:” H:, and enter as Folder:
\\fs.ist.ac.at\dfshome\[username]
where [username] is your IST Austria username.

Ensure “Reconnect at sign-in” is selected, and press “Finish”.
H:\ is now connected, and you can do the same for all other drives/shares if needed.