Since you posted this in "Other", which product's gear are you looking to try?
Either way, you can find the how to demo gear FAQ at
https://www.ikmultimedia.com/faq/index.php?id=970 which tells you that you need to keep the Custom Shop application open and be connected to the internet to try gear.
You should see your gear available to use in either AmpliTube 5 or T-RackS 5 if you are following those steps/guidelines (and make sure you have the latest version of the software installed).