No random tests.

fixed by a fork

I have this exact problem as well. The full error text I am seeing when running the full Attempt is:
/home/codewarrior/program.fsx(89,6): warning FS0058: Possible incorrect indentation: this token is offside of context started at position (83:6). Try indenting this token further or using standard formatting conventions.

/home/codewarrior/program.fsx(96,5): warning FS0058: Possible incorrect indentation: this token is offside of context started at position (89:6). Try indenting this token further or using standard formatting conventions.

/home/codewarrior/program.fsx(103,5): warning FS0058: Possible incorrect indentation: this token is offside of context started at position (96:5). Try indenting this token further or using standard formatting conventions.

/home/codewarrior/program.fsx(55,17): error FS0039: The value or constructor 'Dictionary' is not defined. Maybe you want one of the following:
dict

Ah you're right - I fixed the signature of the solution.

but this kata does both directions (number -> roman numerals and roman numerals -> number), while the other one doesn't

The F# version of this kata also seems to be broken - the sample tests work fine, but the "attempt" tests throw errors with (hopefully) correct as well as placeholder implementations. The errors thrown reference line numbers that don't exist in the solution code, and complains about "Dictionary" not being in scope, even though the solution code doesn't reference "Dictionary".

just a tiny nitpick - in the 'solution setup' section, both args are named 'words'