Check for any visible molds, I'm sure you've seen what happens to a glass of water when left out for days. If it's just started it could look like tiny specks, in all sorts of potential moldy colors.
Also check for fermentation, which has very likely occurred. Signs are fizziness (think beer or even champagne maybe) and a distinctly sweet smell IME. The smell fermented is probably much better than just harmala tea, and actually may not be bad to drink (don't do it because I said it was ok tho) as I have read on the Nexus from reliable sources actually that ayahuasceros will sometimes ferments their brews to make them more palatable, and in some regions this may be the rule rather than the exception. I mean, think about it, it would be hard to keep a (somewhat) sugary caapi brew FROM fermenting at equatorial temperatures!
And if you want to get rid of any alcohol that may have formed, as well as any microbes colonizing your brew, just boil for 5-10 minutes. Dunno if that changes the taste, but fermented is probably "better".
If you don't notice either, I'd say drink it. I used to live in my car and had brews unrefrigerated for weeks and they would stay good. and to be honest I don't ever remember a time that I've had a harmala brew go bad - but then I often would just eat the seeds raw so I dunno. I've drank fermented Jurema and it was weird, actually seemed to change the effects, making it much less visual and heavily somatic.
Anyway, hope that helps.
بسم الله الرحمن الرحيم
Fairly responsible Kratom user.
"whenever he drank ayahuasca, he had such beautiful visions that he used to put his hands over his eyes for fear somebody might steal them."
in between the grinding-brakes of a train crash while aluminum-foil robots make obnoxious sex noises on a static-filled walkie-talkie radio.