Are Pavlovia credits reserved every time the 'ok' button is clicked?

Description of the problem:
I received an error when my participant tried to start the experiment: after clicking ‘ok’, the screen said ‘initialising the experiment’ but did not progress to the experiment. I got them to close the experiment and re-open the same link. In the meantime, I released the reserved credit on Pavlovia, thinking that this was reserved for the experiment that had not worked correctly, and I wanted this one back in case of further issues as I did not have many credits left.

The second time the experiment was loaded it worked (I still have no idea why it sometimes randomly does not) and I assumed that when my participant clicked ‘ok’ to start the experiment a second time a new credit would be reserved.

However, it seems no credit was reserved and after my 2-hour experiment, no data was actually saved. So, I am wondering - when is a credit actually reserved? Why was a new credit not reserved in the time between me releasing the previous one and my participant running the experiment a second time?