This ordinarily shouldn't be necessary, but apparently the Game.GetNthModDependency() function (which Trade Routes uses to find compatibility plugins without some futzy polling or callback scheme) was commented out back in SKSE64 2.0.9.
PLEASE NOTE: This beta release includes an update to Game.psc/.pex based on the copy from SKSE64 2.0.19.
I'm happy to (finally) announce (at long last) the beta availability of Trade Routes - Regional Economy SE for Skyrim Special Edition.