What has worked for me is inserting the tab first, and then the rest of the speaker cover followed by the screw. Though, I'm not so sure you can insert the tab first with the A pillar still attached... It's a pain trying to get the covers back on with the A pillar still attached, but I have done it a few times after some struggling. But it's quite easy with the A pillar removed if you want to go through the trouble. If not, you'll just have to try many angles until you get it to seat properly.

Good luck