Every time you trigger an execution of the workflow now, it will end up in the Queue. You can only run 5 workflow simultaneously in your plan. If the workflow takes around 300h each, it is around 13 days - so only every 13 days a slot in the queue frees up.
Start by cleaning the queue - stop the pending jobs.
Then check the workflow, run time of over 300h is very long. Consider adjusting it, maybe splitting into smaller chunks to make it executable.