article cls problem

[spadekevin]

HI,

I´ve installed Lyx recently in my computer, every time I try to open a Lyx file it reports the "Standard Class Article requires external files not available" The requisite is the article.cls file. However, when I go to the miktex packages files the article.cls file is already there. How can I fix this error message so that my file compiles?

Any help will be apprecited.

I didn't find the right solution from the Internet.

References:
https://latex.org/forum/viewtopic.php?t=31339
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Thank you.