If you've got multiple PC's or gaming devices, like my Steam Deck & ROG Ally, the Steam Network File Transfer system that allows you to copy game installs over your home network rather than having to download them again via the internet is great!
Unfortunately it doesn't always work, or stops working and starts downloading, so in this tutorial video I share some hints and tips to fix & repair the process if it hasn't started in the first place, or stops working during a game transfer install process.
I find the best way to install games from device to device reliably is to make sure both are on the same wi-fi network, restart the mobile device (in this video my Steam Deck), then pause the install, then restart it.
If the "donor" machine goes to sleep, the connection will be lost and the install will revert to downloading over the internet, so make sure you change the power settings on the donor so that it stays awake during the entire process, but if it's a hand-held pc make sure it's plugged into a power source.