I tried to set the max level to 150 on an ark server. It looks like it worked. The server restarted and the max level button is checked and reading 150. However when I go into the server and use addexperience 1000 0 1 the max it sets me is level 75. I can use the command over and over and I see my total experience increasing but it never levels me past 75. What am I doing wrong?

You're actually not doing anything wrong.

But it appears you're not familiar with the ARK Leveling system.

ARK leveling accounts for all 4 leveling methods:

60 combined levels for defeating the final Boss on The Island, Aberration, Genesis 1, and Genesis 2.
The first time you kill a boss, depending on the difficulty you recieve either 5, 10, or 15 levels. If you defeat a boss on a higher difficulty level, you only receive the difference in levels.

5 total levels are earned via the use of Chibis.

10 levels are earned via explorer notes from Genesis 2.

That's a total of 75 levels that cannot be earned by experience points.

The remaining levels are then earned via normal experience gains.

I am familiar with the leveling system. By changing the Overide Max character level to 150 it means I should be able to achieve level 150 without defeating any of the ascention bosses. In fact if I preview the Game.ini file the levelexperienceoverides command is in there configured from level 0 thru 148 and the overridemaxexperiencepointsplayer is also configured to match what the override for level 148 is. What that means is I should be able to normally advance to level 150 without doing any ascention fights but it won't let me advance past level 75 so something is wrong.

No. That seems right. 

150 - 75 ascension levels = 75 levels achieved through experience. 

There is actually a bug or something going on. My friends and I were all around level 85 and doing fine, then one day recently logged on to find ourselves all locked at 75. This hasn't happened on servers with other hosts, this is something to do with Ark Servers themselves.

Shouldn't be. Your characters sound like they were normalized based upon your max level settings. I've tested on two servers now, one modded and unmodded. The levelling system works as documented on the ARK Server configuration page.

https://ark.fandom.com/wiki/Leveling

Which mentions that without ascension, the default cap is level 105, with a maximum level of 180 via Chibi, Exporer Notes, and Ascension. Prior to Gen2, the default exp level cap was default was 105, and a maximum level of 155 with 50 levels via Chibis and Ascension. 

What's probably occured, is the other hosts you're using is sticking with the ARK default level, with 0 adjustment. So when ARK updated, your max level also increased to 180 alongside it.

Here, if you have your max level set to 150, as that's a player defined option, it stays at 150. 

And again, 150 - 75 = 75.