Reproduction steps:
1. Open the attached project "AddressablesBug.zip"
2. In the Project window open Assets/Scenes/SampleScene
3. Enter Play Mode and observe the console message "All is working. Good job :-)"
4. Exit Play Mode, turn off the internet connection and enter Play Mode again

Expected result: Console has the message "All is working. Good job :-)" and 2 Content Catalog files are cached
Actual result: Console doesn't have the message "All is working. Good job :-)", errors are displayed and only 1 Content Catalog file is cached.

Reproducible with: 1.15.1, 1.16.13(2019.4.15f1, 2020.1.14f1, 2020.2.0b13, 2021.1.0a7)
Couldn't test with: 2018.4.29f1 (Missing assembly references when downgrading)

Notes:
- The issue reproduces not only when offline, but it can also cause issues while being online as well, however, this issue reproduces easily while being offline, the offline mode is just specific for this repro project