Backtest-Error-Could-not-compile-the-strategy-null-Executor

And how do you expect us to troubleshoot your compilation error without your code?

QUOTE:
Backtest Error: Could not compile the strategy (null Executor).

Okay, why don't you show us your Execute{block} C# code for starters. Here's a sample.

CODE:
      public override void Execute(BarHistory bars, int idx)
      {
         if (HasOpenPosition(bars, PositionType.Long))
         {
            //sell conditions below
            
         }
         else
         {
            //buy conditions below
            
         }
      }

The strategies that became corrupted and can no longer be back tested were ALL "Block Strategies". I never said they were coded strategies.
Sorry I did not read your mind about this.
I do not code.

I'll try to figure this out myself, Thanks

It's hard to help only having the symptoms and no evidence. It might help to know which elements (blocks) are used. Aside from that, I suggest upgrading to the latest builds for WL and extensions.

I think I solved this problem, and below are the changes I made to all the strategies affected on my end...
Yesterday I was running and comparing four separate scalping strategies to the WealthLab test account. These four strats place a fair number of orders per day on the 1-Minute time frame. When yesterdays update #160 was auto received, these strats stopped behaving normally, which is typically the case when an update is received during the trading day, so I deactivated the strats and then installed the update. Now, none of them worked at all, as reported above.

Each strategy contains two blocks using RSI as a conditional symbol ranking block. When RSI is replaced with a different symbol ranking indicator (Momentum, for example), the strategies are repaired.

So, my presumption is that the update changed the way RSI is used.

Thanks, good to know.
I'm not aware of a change that would have affected it, but probably just making any change and re-saving/activating the strategy would have fixed it. Try going to back to RSI now.

Update -
Actually, there was an innocuous change to the icon for Weight condition. Honestly, I don't know how that could have affected a strategy, but maybe that was enough to do it.

That's the first thing I tried, but no go.
And changing it back again to RSI simply recreates the error.

Can you open the strategy as a code based strategy, try to compile it, and send any compile errors you see?

Sure, here you go....

Compiled at 3/11/2026 16:51:50
37: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
41: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
195: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
196: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
235: The field 'MyStrategy.valRank' is never used
239: The field 'MyStrategy.rank' is never used
237: The field 'MyStrategy.cacheKey' is never used
236: The field 'MyStrategy.bhRank' is never used
254: The field 'MyStrategy.value2' is never used
255: The field 'MyStrategy.trailing' is assigned but its value is never used

QUOTE:
37: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
41: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
195: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'
196: 'RSI' is an ambiguous reference between 'WealthLab.Indicators.RSI' and 'WealthLab.MyIndicators.RSI'

Well, there are several possible fixes for C# code. But if you are using Blocks, I would rename your WealthLab.MyIndicators.RSI to WealthLab.MyIndicators.RSI2 so there isn't a name conflict with WealthLab.Indicators.RSI proper.

Do you really need both RSI definitions in the first place?

It looks like you created a custom indicator named RSI, delete that custom indicator, restart, and you should be good to go 👍