If you see a warning about insecure content (or nothing!):
Check you are using https://secure.clublog.org, and not http://www.clublog.org in your iFrame. This is necessary from 7 July 2015 when QRZ.com switched to HTTPS.
If you see "Feature not enabled":
You must enable the Last 10 QSOs feature from your Club Log profile. This is an option in Club Log itself, which is disabled by default for privacy reasons. It is located on the Settings page in Club Log. Look for the label "Activate the last 10 QSOs and stats tool on your account?".
You must also ensure your callsign is not hidden. This is explained here: http://clublog.freshdesk.com/solution/categories/59695/folders/97594/articles/53209-why-doesn-t-my-callsign-appear-in-the-leagues-and-log-search-tools-
If you only see source code:
If you see the source (ie. the code, and not the search filter) make sure you use the Source mode in the QRZ.com biography editor. It is in the top-right hand corner of the editor. If you don't use source mode, you will see the code in your profile.