Cant download media to imovie timeline

I am not able to select the media in imovie for edit. Even after clicking the file the tick mark is not coming and randomly at somepoint the clip got tick mark and get imported but the next moment when i try to get the next clip the same thing repeats i wont be able to select the clip. I thought it was because of the cloud upload download timing so i turned off the photo sync(i am not sure if its right thing to do) and tried again but the same happened again. Did any of you guyz know the solution for this? Thank you in advance