iMessages & next best thing to being forced to accept.

Reading the grey print ~ I really do not to reproduce the (for me) the problem. I have not had to use iMessage until 10 days ago. A big ole Green shield pops up and will not use my msgs, till agreed to accept it or be shut out for ??????? However 10 days before that w/o notice or warning when I went to message someone the name turned red & the blue send button would not show. Went thru 90% of my contacts some have iPhone's others Android & got no where. this is from my iPad Air 4 5th Gen. And before I signed up for I read lots of solutions but after Settings then Message the info on the screen didn't match any thing my pad was showing. So to get around this iMessage boot camp Sargent what protocol is needed? Half the people in my contacts rarely look at their email & 5 days go by before they answer. Plus 1 day a week I have an on line job that requires me to text the client so this iMessage thing has tied at least one arm behind me back. So to speak I be all ears or eyes. GalaxieDude PS me phone is an Android, sorry :/