Nobody's listening to you.
About a year ago, Facebook throttled back on how many of your supporters see what you post on your page. It's been disastrous for many groups who've depended on their Facebook community for donations and support.
It's still a problem for many, but there are several ways you can counteract the new policy.
First, about your email list -- wait, what? You DO have an email list, don't you? Outside of Facebook?
If you don't, that's your first priority. All your old adopters and applicants and other people who've emailed you. If you've been taking donations on PayPal, download those logs and put those donors on your email list.
You must do this. Must.
So. Now that we have that settled -- start staying in touch with your community. Email at least twice a month, just letting them know what's up. I don't care if you use a nice Constant Contact template or a plain text email via MailChimp (usually there's a free account for most small nonprofits). You have to stay in touch!
Second, use your page. Post at least every two days. Ask people to click LIKE on your posts. Ask them to share. Facebook treats that as engagement and will increase the visibility of your page posts in your audiences' newsfeeds.
Third, periodically remind your LIKES to check their notifications. They should be asking to see everything that's posted.
Finally -- and this one is going to be a bit complicated -- place a Facebook pixel on your website. It's a small bit of code that acts like a cookie and enables you to reach out to people who've visited your website. There are some other slick things it does as well, like enabling you to create look-alike audiences. More on that in my next article. Facebook has some super help files on how to do it if you're the sort who likes to forge ahead.
Yes, I'm talking about advertising. No, it's not free. Yes, it's inexpensive and very much worth it.
Bonus tip: check out the Google Adwords for nonprofits. Ton of value, worth learning to use.