@Jinx, try restarting your computer and then verifying the integrity of the game cache for Arma 3.

1. Restart your computer and launch Steam
2. From the Library section, right-click on the game and select Properties from the menu.
3. Select the Local files tab and click the Verify integrity of game cache... button.
4. Steam will verify the game's files - this process may take several minutes.

Tried your solution didn't work

im not opted into any betas if that helps

But even when i wasn't on a beta it worked before i downloaded apex

@Jinx, please prepare and upload a troubleshooting report via the Arma 3 Launcher for the developers to review.

For issues regarding Arma 3 you can file a troubleshooting report, also via an action available in the option menu in the upper right corner (gear icon)

Be sure to upload the whole report file. If the report file will not upload directly to the feedback tracker then try uploading to a free file sharing service such as Dropbox, Microsoft OneDrive, Google Drive, Mega.nz, and so forth.

ok i did

Where can i see if it was fixed?

Can you attach or link the report file in a comment below?

um i already filed it so where would i find it?

When you prepare a troubleshooting report via the Arma 3 Launcher it prompts you to choose where to save it. This should be in Libraries\Documents by default.

Wait, i just fixed it i switched to legacy port and it loaded up.

I have figured out a better way to fix my problem and i believe it could help others

So for those of you with my same problem you may get his error message: Bad Version 72 in p3d file: a3\vegetation_f_exp\clutter\grass\c_grassbunch_hi.p3d.
Well instead of having to re download content to switch to legacy branch try this.

So take your mac and go to finder. Navigate your way to library then open application support. Find the steam folder and go to steam apps and from there to common. Find the arma 3 folder and open it. Scroll down to Expansion and open it then open addons. Now find all files in the folder that contain the word vegetation as this is the problem file. Now move all these files to your desktop and leave them there. Go back to steam and play arma 3. You may open it and load in or it may say Bad version 72 in tanoabuka p3d file. Do the same steps to get to the expansions folder and addons folder as described before. But this time move all files containing the word tanoabuka to the desktop. Now your arma 3 should run fine. This worked for me and let me know if it works for you.

I could find a better place to put and now i leave this for the admins of these forums to spread this help to other but do warn them not to delete the files as once this is fixed they should re-enter the files to their folder as these could be essential to playing the tanoa map.