Syntax highlighting and plotting problems with Jupyter Notebook

Hi,

sometimes Jupyter Notebook loses the syntax highlighting for my Julia Notebooks. Addtionaly then I´m also unable to plot. I´m working on Julia 1.2.0, IJulia v1.20.0, WebIO v0.8.11 and Windows 10. I followed several instructions on different sites to solve the problem, but nothing works. Does somebody have another clue what to do?

Furthermore I get following message during start of Jupyter Notebook:
WebIO.jl will not work as expected. Make sure WebIO.jl is installed correctly (try running Pkg.add(“WebIO”) and Pkg.build(“WebIO”) from the Julia console to make sure it is).

Sites with instructions to solve the problem
https://github.com/JuliaGizmos/WebIO.jl/issues/236
https://github.com/jupyterlab/jupyterlab/issues/6826
https://github.com/JuliaGizmos/WebIO.jl/pull/286

Somehow the problems just occur for Jupyter Notebook and not for JupyterLab.