Web partnership

Faced a problem and want me to explain that I am not doing so :)

So, in November last year, I launched the Internet service It's time to congratulate (mydays.ru). The idea is simple - to remind service users of the upcoming dates of their friends and acquaintances. Honestly, I tried, did for myself, ordered the design, AJAX, import / export, all that ...
Users rated like, enjoy. Recently, the daily sending of reminders reaches letters of twenty a day, the user base is growing.
And I decided to use this case for personal enrichment :)

I chose a list of shopping sites that are engaged in gifts / holidays, and wrote there an offer of cooperation. I supposedly can add links to your products in my newsletter. And I know something about users, so you can make certain offers, depending on the user / event.
And in response - silence, only one reaction, and then with refusal.
')
Does this mean that sites are not interested in collaboration? Or am I doing something wrong? Are there any examples of successful cooperation?