I totally understood what you said, because I met with this issue for many times, and until today I solved it, check this post. :D
https://www.snbforums.com/threads/rt-ax86u-pro-astrill-vpn-applet-issue.83302/page-2#post-885866
Hey, maybe you can check this answer, I found there seems like a same issue:
- disappearing file: openvpn
- disappearing Astrill applet interface.
https://www.snbforums.com/threads/rt-ax86u-pro-astrill-vpn-applet-issue.83302/page-2#post-885866
Hey guys, I have solved this issue.
I think the reason is Astrill applet lost the file "openvpn" with a mystery reason. If you have entry the astrill folder, and you can find the file "openvpn.conf", and "openvpn.log", but there is no file "openvpn". And I can say definitely we have a same...