08 Chevy cobalt (manual) won't start

My guess is that you knocked off a vacuum line or electrical connector. Check for a disconnected vacuum line or connector. Yellow gunk under the oil fill cap is fairly normal in winter and spring. See this post on yellow gunk under the oil fill cap. https://ricksfreeautorepairadvice.com/yellow-gunk-under-oil-cap/

Thanks I will give that a shot, im also having the starter tested. Much appreciated :)

Check that all the grounds and connections to the battery are tight and clean. Load test the battery as well. It may have enough power to run accessories, but not enough to turn over the starter although boosting it usually (but not always) overcomes that. Anyway, trouble shoot first.... buy parts later.

It was something with the battery connection.. Thank you so much.