Hi,
I had a busy week-end, too, trying to get Mathematica running. The connection frontend to kernel seems to be broken like so many other users described it here. I sent an error description to the service desk and got an answer in short time (thank you!).
As many other perople are experiencing this problem, here ist the proposed solution:
We made a few updates to Mathematica last week which resulted in your installation not being able to launch
the mathKernel as normal in versions 11.1.x.
Please close any instances of Mathematica or WolframKernel that are running in the background.
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a) Launch WolframKernel using the following step(s):
For Windows:
Start menu -> Search for 'Mathematica 11.1.1 Kernel' and launch it
For Mac:
In Finder -> Applications -> Right click Mathematica (control click) -> Show Package Contents -> Contents ->
MacOS -> Double click WolframKernel
For Linux:
In Terminal evaluate: /usr/local/Wolfram/Mathematica/11.1.1/Executables/WolframKernel
b) In the launched WolframKernel evaluate
PacletSiteUpdate /@ PacletSites[]
PacletUpdate["EntityFramework"]
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If you are still encountering issues after following these steps, please let us know.
Sorry for any inconvenience caused by this issue.
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