For any EA you make ... Before allowing a new order to be placed, we need to check first if there is an already pending open order or an open trade.
Once per bar is probably not a good idea. If you use your EA on more than 1min chart ...a bar can be very long and a lot can happen in that time.
You also want to use a time filter.... (if you want to sleep well...hahahah) I trade for example DAX and I want my EAs to work only during Euro and US market times.
My subtraction of high - open is rather for a shooting star than a hammer ... sorry. But the logic is the same .
Be careful ! Metatrader is not good in making a chart of Renko. It creates BRICKS that look like candles .... BUT THEY ARE NOT. In a Renko chart (on MT4) the values for open high low close are useless. The only value that is correct is the close value, at the instant of closing (formation) of the brick ONLY. If you make an EA that use "once per bar" it will react on the bar open. But this value is only created retrospectively in a Renko chart. If you want to invest time in Renko ... make EAs that ONLY take the brick close for action ...(good luck with that)
https://fxdreema.com/help/working-with/magic-start-and-groups
There will be an other reason why the EA does not trade. We can even give trades from the same EA a different MN by using the Group Number (the upper parameter you find in every block).