Based on the photo, it appears the wiring is correct, assuming the orange and brown wires are inserted sufficiently deep into the header as to make a connection with the contact down inside the hole).
Your code is different from the latest a_wild_card.ino example that we include with the current SDI-12 library files. Are you using an older example sketch or an older library? We had to make changes to the library last year in order to work properly with some Meter Group sensors, so perhaps you just need to update your library and/or try the simplified sample sketch that’s included with it (https://github.com/EnviroDIY/Arduino-SDI-12/blob/master/examples/a_wild_card/a_wild_card.ino)
Also, Meter Group sensors come from the factory with SDI-12 channel ‘0’ assigned to them. You should change it to something else first (using the “b_address_change” sketch) because they operate in a TTL protocol when they’re set to channel ‘0’, so if you intend to use them as an SDI-12 sensor, changing them to a number (or letter) will cause them to work correctly with the SDI-12 sketch, assuming you put that new channel number into the wildcard sketch.