It seems you're using --module commonjs. I modified Fable so in that case the default reference to the coreLib is fable-core/umd, I guess I should removed that if you're using it together with --rollup (as Rollup only understands ES2015 exports). For now the solution would be to remove --module commonjs and use "format": "cjs" within Rollup options instead.
Oh yes, I didn't see the module line thanks
Latest version (0.7.22) should be able to bundle normally even if you use --module amd. Can you please check?
It's working :)
Thank you.