Moz's tools can give a page any score, but it doesn't mean Google will rank it in a lower place than it deserves. If your page has an 'F', maybe all the other pages on that SERP do.
Your page may have good link authority or a good balance of anchor text links which could assist its ranking. Have you considered linking factors?
The report which gave you your score for the page should outline changes you can make in order to comply with SEO best practice.
Final thing - I'm in the UK but couldn't see you on page one for "social media marketing edinburgh" (logged-out, incognito-mode chrome session with personalised search off, location set to Edinburgh).
Thanks,
Rob