Guests lose access to space that was previously working as expected

[Emile]

Hi

My guest users that were able to sign on and use the space to which they have been allocated are losing access. 

There is no obvious indication as to the reason for it: They appear on the Atlassian user admin screen with guest access, and also still appears on the space access screen with the guest role. 

My searches lead me to Security -> Security guide -> User security, of which all settings & info is hidden behind an upgrade add-on. 

From the Jira admin settings all the guest users are marked active.

We are well within the limit of the licensed to guest user limit. 

Any ideas?