Withings BPM Connect - Error 203

Hi, 

I just bought a Withings BPM Connect. I followed the instruction, and tighten the cuff around my left arm. The tube faced to my chest (inner arm). 

I turned it on and then it started measuring the BP, but the cuff was getting wayyy tooo tighttt, but I tried to hold it. At the end, the measurements were always showing error 203, which I found out on the page - it couldn't read HR. I tried it multiple times and still didn't work.  

So what should I do? 

Thank you in advance.