Are you trying to attach a tech beacon to an arcane teleport and is that maybe the issue? (I'm only starting to dabble in bases myself so I don't know if it's possible to mix and match the two types of teleports with the two types of zone beacon).
Defiant 50�s: Generalissimo, Righteous Bob, Splortch, Brutus Cayuga
Union 50's: Chimera Obscura, Diet Anthracite, Grim Proctologist, Puny Little Minion, Raging Bitumen
In Soviet Russia, mission farm you!
D'oh! Spot on! I'd even noticed the beacons I was trying to attach were tech-style, vs the rest of the base being arcane. But had assumed tech was the default beacon style, and it would change to the "correct" type as soon as it was attached to something.
Switched to the Arcane Teleport tab, created a beacon from there, and it worked first time. 
Thanks Gen!
Glad to be of help 
Defiant 50�s: Generalissimo, Righteous Bob, Splortch, Brutus Cayuga
Union 50's: Chimera Obscura, Diet Anthracite, Grim Proctologist, Puny Little Minion, Raging Bitumen
In Soviet Russia, mission farm you!
I've recently started dabbling in bases, mainly for a small VG with half a dozen members (who are mostly my alts), and so far have a fairly standard small base/transport hub setup. Oversight Centre, combined power/control unit, "second from smallest" TP room, 2 teleports and 4 anchors.
As of this morning that was working; the 4 anchors went to the 4 lowest level villain zones, and everything was just inside the power/control units limits.
Then my highest villain in the group got the Nerva beacon badge, I tried to swap that in to replace the Port Oakes one, and problems developed. The Port Oakes beacon deleted fine, and I could put the marker for the Nerva beacon in the base, but for the life of me I can't get the beacon to attach to the teleporter.
The teleporter's info indicates it's now only got 1 of 2 devices attached, I've tried putting the new beacon in the old one's position, in an unambiguous slot on the wall to the left of the porter (see screenie for TP room layout), dragging the beacon onto the porter and vice versa and looking for anything hopeful on info dialogs. No joy
If I delete the Nerva beacon and try to re-attach the Port Oakes beacon, I get the exact same problem.
All input on the obvious solution I must be missing is welcome!
The next question's far less specific; with the base as described above, it's near enough maxed out on power and control; I'll need more of both if much more in the way of kit's to be added. A quick test showed you can't add another Oversight Centre and power/control combo to a base, so I'll have to move up to dedicated power and control rooms. But...how expensive are these!?
While the initial Oversite plus power/control setup costs 75k, it looks like it costs 400k+ to move to dedicated power rooms + source and control room + source. Is it really such a big step up, or am I overlooking something?