Your battery is too low. This is the same issue that was asked about last week: https://www.envirodiy.org/topic/battery-failing-in-the-middle-of-the-night/
Anytime your battery voltage drops below 3.55v, the logger won’t transmit, in order to save battery power and conserve enough energy to keep writing the data to the memory card even though it’s not transmitting. It appears you station is extremely shaded since your battery voltage has been extremely low since June. Sometimes we see this in stations that have a lot of leaves during the summer, but the issue usually resolves itself in October once the canopy opens up and allows more light. You could also just buy a second Lipo battery and charger and swap them out a time or two during the summer to keep things at a higher level. You could also try increasing the size of your solar panel, however it’s usually easiest to just swap batteries during the summer, because you should be visiting the site regularly for cleaning or routine maintenance, so you can just swap that battery when you’re there, and also retrieve the data card which will contain any missing data that wasn’t transmitted.