I am trying to capture stereo audio with two lavalier microphones. The microphones are the Rode SmartLav+, which has a 3.5mm jack that I believe is TRRS, it works directly with phones. My audio recorder is the Tascam DR-40X, which has two ports which take either XLR or 1/4 jack. My assumption was that I could adapt the 3.5mm to a 1/4 jack with no issue, but that proved not to be true. Since then, I have tried using a stereo to stereo adapter and a 3.5mm stereo to 1/4 mono adapter. Neither produced a signal, so I got TRRS to TRS adapters, and tried again with both the 3.5mm to 1/4 adapters, again with no signal. Is there something I am missing? Or are the two ports on the recorder not mono? Let me know if there is any useful info I can provide, I am very new to audio.
The Rode SmartLav+ is a high impedance [high-Z] mic, suited to computer headset/mic inputs. It also sounds like the pin-out of TRRS is designed to not confuse a computer's headset input. It's not really built for pro audio.
Your Tascam, based on the plug input types [I can't see any real spec on their web page], is expecting a professional low impedance [low-Z] mic.
I really don't have much experience of consumer-type mics.
Low to high-Z transformers are common, but I'm not finding anything for high to low-Z. https://www.thomann.de/gb/special-adapters.html has reams of adaptors of varying types… maybe you'd find something in there. [I have no affiliation with that particular store, just that Thomann is just one of the biggest musical "box-shifters" in the EU, so they're always a good place to look for things.]