Missing Series X internal SSD

Microsoft does not sell components to end users ans we cannot assist with self repair. There is no way for the end user to fix this.

If they didn't advise you of the missing SSD i suggest you return it,

Are you using a Series S/X?

Series S/X optimized games can only run from the internal SSD or an expansion card made specifically for the Series S/X.

Not really...

Xbox Series X games / upgrades / updates has to be installed onto the Series X internal or expansion card SSD,

You can have Xbox One games on your external hard drive that will get an Series X upgrade but the games will need to be transferred to the Series X and then the Series X upgrade will need to be downloaded onto the Series X SSD,

As an example...

I have Marvel Avengers on my external hard drive that will get the Series X upgrade and I will transfer the game over to the Series X SSD ready to download and update the game to the Series X version when available.

Try recording directly to the Xbox Series X internal SSD, to see if the same issue happens, please.

If they were to put it a bigger ssd internally the price of the series x would rocket so to keep prices at a reasonable level these 1tb ssd drives sold separately and you only need them to play series x games once the internal ssd is full however you can
still use standard external harddrives to play xbox one 360 and og games from and yoi can also store series x games on them you just cant play the series x games from them so it might mean a little more transfering around of series x games (which will move
much faster than hames move now) so for a fair while you probably wont even need the plug in ssd drive.