@MOS-FET Same problem here too. I got a couple of the Heltec Cubecell’s, I fired it up with the sample code, set it to 915mhz, and it just worked and thought it was amazingly simple. Then 19hours later it just stopped… I saw a couple partial joins, then it’s never joined again. I pulled out the 2nd one, known good 900mhz antenna, same issue. It’s really discouraging. My other nodes are working fine, so I suspect my gateway is running fine.
EDIT: Yes I tried different pigtails and moving between 3 - 20m from the gateway.