It is never a bad idea to have a bootable USB with a system on it that you can use. While I would guess that the use case considered here would be to use such a system on your own computer, it may also be possible to use it on other systems.
However, if you intend to use a "not your own computer":
Boot Issues: If you're having trouble booting into Tails OS, make sure your USB stick is properly inserted and that your BIOS settings are configured to boot from USB.
If the hardware machine's BIOS disallows booting from USB and is password protected, no bootable USB system will work for you. You can check to see by attempting to enter the BIOS during normal boot and checking the boot options (as long as there's not a password in the way).
Network Issues: If you're having trouble connecting to the internet, make sure you're connected to a network and that your network settings are configured correctly.
Similar to the above, the network you are connected to may have security configurations which prevent a network adapter from connecting to either a wired or wireless network unless it presents an authorized MAC address.
This kind of thing isn't "the" answer. If you have data to share, you're still going to have to figure out a way to safely exfiltrate it, then use a bootable USB system as one layer of subterfuge.
Tor Network: All your internet traffic is routed through the Tor network, which helps to conceal your location and identity.
You should still not use your own network, or any network which can be connected to you personally. Libraries, cafes, any public internet is vastly preferable. Drive a long way to do it, maybe do it from public internet while on vacation (bonus points for vacation outside the country).