There needs to be some separation between the blue boxes when you have poll once per activity period is checked. Your activity period is solid from 06:00 until at least 10:00
You may also uncheck Poll once per activity period. As Uomo rightfully mentioned, you have an all solid selection, which means that it will run only once per block, i.e. at 6 AM, then wait for 6 AM the next day.
With this you can leave the blocks selected as they are. Once this is done, have the Polling interval field set to 15 minutes.
This will make your process active every 15 minutes betwee 6 AM and whatever time the block ends.
I tried this. But the issue I’ve come across is that with polling set at 15 minutes, this seems to be based on whenever the workflow service restarts so if the config is updated at say 9:08 the poll won’t run again until 9:23.
I was looking at each of those 15 minute blocks as an individual block not the whole.
I have a work around but was trying to limit the amount of unnecessary activity.