Scans are not working at all right now. I tried last night after Friday's market closed and tried again, Saturday morning. Whenever you have a question about why a particular scan is not working, be sure to check that the scan engine itself is functional.
I do this by running the following scan:
plot scan = close > 0;
If you get zero results, the scan engine on Thinkorswim is broken and you need to contact TDA support. So check if the scan engine is broken first, than just give them that line of code and tell them it's producing no results at all.
Update: The test scan I provided above has started working again. So I tried building a scan for RelativeStrength using the Condition Wizard. This also produce zero results. I have sent a request to TDA support using the Message Center under Client Services of the TDA web portal. I will keep you posted on any response I receive. Below is the code I generated using the condition wizard and sent to TDA support for evaluation:
RelativeStrength("correlation with security" = "$DJI")."SRatio" is greater than RelativeStrength("correlation with security" = "$DJI")."RS"