A blinking red light on an iClicker+ remote indicates that your vote has not been received by the iClicker receiver.
The iClicker is not on the correct frequency
iClicker+ remotes pair to receivers with a two letter frequency code. By default, this code is AA. To avoid interference between iClicker receivers in classrooms, some instructors use a different code. When you turn on your iClicker+, two green lights will flash corresponding to the frequency your iClicker+ is on. For example, if you turn on your iClicker+ and the green light next to A blinks twice, you're on frequency AA. If the green light next to D blinks once and the one next to C blinks once, you're on frequency DC. If your instructor hasn't told you you need to change your frequency, then you'll likely be using frequency AA. Instructions to change your frequency are on the back of your iClicker+ remote. You must be in class and the iClicker software must be running before you can change the frequency of your iClicker+ remote. The current iClicker+ remote will remember the frequency after being powered off.
Polling is closed
If the software is open but the polling is closed (the poll hasn't started or it's ended), your response will not be received and your vote status light will blink red.