These Ethernet shields are quite unreliable. Just because you’ve changed to another doesn’t mean that you have a good one.
If the LEDs on the Ethernet shield are flashing very quickly then keep nigg8ng th Ernest button until you get a clean reset.
Take a look at the main chip on the Ethernet shields and look for solder bridges between the legs - you might be surprised!
Also, these shields won’t work with some Ethernet switches, so if you’ve changed any other hardware then that could be a factor.
See this thread:
In the long term, you might be better going for something like the Wemos D1 Mini instead of the Arduino and put a wireless access point in your greenhouse to give Wi-Fi coverage for the Wemos.
Pete.