My blanco kitchen mixer does not swivel. It is stuck in one place

My Blanco kitchen faucet has a set screw at the back just below where the spot pivots.

Epoxy resin will fix that, or buy new.

see diagram...
https://blancotapspares.co.uk/blanco-cleo-ii-chrome.html
cap (6) and screw (5)

You simply use a punch and hammer and tap it out.

I boiled the kettle, added the hot water to a tray and placed it in the oven, shut the door then left it for 10 minutes so it steams up the oven (make sure power is off first). Do the same again. Then get a multi grip spanner and place a kitchen rag over the cover and turn to the left. It does take a bit of force depending on how stiff it is, but the steam will loosen the cover. The steam also cleans the oven quite a bit too!!

The button doesn't move. You must push the beater up beyond th notch and turn it while pushing up.

The spouts normally take an "O" ring seal and these should be freely available at larger hardware or faucet outlets. There may also be a plastic wear ring which does not seal and is not normally replaced unless the spout is loose in its fitting.

Check fine filter at tip, probably blocked, got caught with same thing myself recently!!!

If the bolt is the hinge pin that the head swivels on when tilting it up, it can be pushed back in when the head latch is released and the mixer head is lifted slightly.

If this mixer sits on a stand, first remove it from the stand. Turn it upside down and shine a flashlight into the right side socket to look for obstructions. When you say you swivel the head, do you mean you rotate the handle? This is how to eject the beaters after use. It may be that the ejector on the right side is stuck. If so, you will need someone with mechanical skills to disassemble & repair.