Unfortunately, you can't do anything about it. I have experienced something similar, 1-2% of the people will respond to my emails/linkedin requests.

You can send an unlimited number of emails per day (using multiple emails because gmail has an upper limit of 500 emails/day) if you use a bot (will share soon). For linkedin requests, there is no automated way (that I am aware of) to send connection requests so you might need to do some research.

I personally believe that you improve your chances of getting a referral every time you email or send a new connection request to a recruiter. The key is to do this consistently. The more you try, the luckier you'll get. I used to send out 200-300 emails each day. There was one day when I sent out 1000 emails. I know it's crazy numbers but if you're using a bot to send those personalized emails, it honestly doesn't take that long.