When the sender or recipient blocks the other person, one of the most common causes of the “message blocking is active” problem. Please double-check your contacts' block lists, and ask the sender to do the same. To check your Block screen, go through the following steps- 1) From the home screen, go to the messaging app. 2) To open the quick menu on your device, tap the three vertical dots that are present in either the top right or the bottom corner. 3) Select Settings from the drop-down menu. 4)Go to the spam filter to see what's there. Then click on the "Remove from spam numbers" option that is available in the drop-down menu. 5)Press and hold the number you wish to unblock for a long time. 6) Select Delete. Finally, press OK.