Using trial build minutes


We’re currently trying out Gitlab, and have been using the Free tier for the the last month or two, but are slowly ramping up. We used up our runner minutes this month, so I thought I’d be able to use the Ultimate trial (we also wanted to look at this to see the features there) to carry on trying this out. However having signed up for the trial on the group, it still seems there are no runner minutes available.
Is there something we need to do to make the Runner minutes available in the project?