Why can't I use "LingQs"?

When I’m trying to make a new LingQs, system say me I’ve reached my limit of lingqs (100 lingqs) but when I change some LingQs to words that I know, still say me I need delete some lingqs, why? What more can I do? Even if I delete the word is removed from all my account and still say me the same! I hope someone can help me. Thanks a lot!

You have created 100 LingQs. Now you need to upgrade.
It does not matter whether you have deleted some LingQs in the past.

What do you want to mean with “now you need to upgrade”. Can you explain me that?

@ElvisPritchard - There is a limit on LingQs for Free users. If you upgrade your account, all restrictions will be removed and you will have full access to all of the features on the site.

We don’t recommend removing LingQs, as these words are kept in your database and sent back to you periodically through the LingQs of the Day; this helps you to review words and ensure you remember them. To ignore a word, you can click on the “X” on the Status bar. This will cause the word to be removed from your statistics.