When I press the tab button to target the next target, my target clears. When I press it again it goes back to the original target. There are lots of other targets around. Why doesn't my tab button go onto the next target? Is there a way to fix this?

are said targets all on your screen? sometimes it will only target enemies within your cameras view so if you only have your camera on one enemy and the rest are on your other side, you wont be able to tab target.

Yes there can be multiple targets on my screen

Go to the options, then look for the select offscreen enemy, make sure its on. Also the tab goes to the same target ie the last one you were shooting at, Shift + tab, switches to the next target, and ctrl + tab switches back to the first target. You can also set these as single hot keys if you want as well as add in another one for selecting the closest enemy.

Tab targeting is useless, better to disabe any "selected" targeting and use line of sight, keeps you from accidentally being locked onto an out of range target and unable to attack anything.

I have to disagree as this is what I use. Many times I can be sitting here trying to click on a target and the game just ignores me.

i recall a thread or two concerning that.

No need to click, when using recticle targeting the game defaults to whatever enemy is directly in front of you. The only change you need to do is set camera mode to chase cam. So what you look at is your target. Works great.

Think of it as ground "shooter mode" in space