I tried gem update jekyll, but it says:
make failed, exit code 1
And it keeps my local version, 3.6.2
you could try doing just gem update which will update ALL your gems. This could be bad though I suppose if you have lots of other gem based projects as maybe an update to some obscure gem would break something? I’m not sure about that. I just did it and it took quite a while and updated a zillion things.
You probably have a conflict somewhere with a different gem - what version of ruby?
My ruby version es 2.4.3