Stuck at guest_step_1 on version 1.2.10

[Ollie]

Having another problem with version 1.2.10:

When checking out as a Guest, I get stuck at guest_step_1. It won't let me go any further.

Why is this happening? How can I fix it?

[Basara]

Hello.
Check:
1. error log for related issues
2. check third-party extensions to make sure they support 1.2.10
3. if you have non-default template make sure issue is not template related