first wrote: I have one more installation of ls206 lts (without https) and limer is working fine with it.
You use the same R script (only destination server different) for both LS installations?
The connection on the working LS installation is established via http and NOT via https.
The connection on the NON-working LS installation is established via https only?
Are both installations on the same server? If no, what differences are between these?
What R / OS environment is used on the client side?
The source of this issue can be a mod security rule issue. That could be triggered by many things.
I would check without https first. Change credentials afterwards. If http is working, you have an issue with the TLS encryption. Which can be a server or client side issue.
If http is not working, it might be a Modsecurity rule, which is preventing the Remotecontrol-API traffic.