Giving thumbs down to no-showing partner: You can give partner feedbacks by going to the room where you will be the INTERVIEWEE and go to the feedback section. There, you can save your feedback. You then mark your partner for no-show and cancel the meeting. However, you can't do this for cancellings with short notice.
About cancellations: I have made 39 back-to-back meetings (totaling 77) and I had about 40 of my meetings cancelled. However, I noticed two patterns with most of my cancellations:
1- When there is a mismatch with experience levels. As a novice, I got most of my meetings scheduled, especially with pro members had been cancelled. As I've done more meetings and gained more experience, I saw less meetings get cancelled.
2- The other pattern I noticed is the time of cancellations. About 60%-70% of my meetings scheduled between 22h00-02h00 GMT+3 got cancelled while my average cancellation rate is slightly higher than 50%. If you schedule meetings to morning time according to Europe, you will probably see less of your meetings will be cancelled.
Overall, I think you had an unlucky streak. My advice is to continue prepping and to become a bit careful with timing of your meetings.