How often and how do I descale my nespresso citiz? I cannot find my manual!

I don't find specific information about this problem. Here are some things to try. If they don't work, you may call beldray customer service. Check the water tank: Ensure that the water tank is filled with enough water and is properly inserted into the mop.
Clean the mop head: Remove the mop head and clean it thoroughly. Dirt or debris on the mop head can cause clicking noises.
Check for blockages: Check for any blockages in the nozzle or steam outlet. You can use a needle or pin to remove any blockages.
Descale the mop: If your mop has not been descaled in a while, it could be causing the clicking noise. You can descale your mop by following the instructions in the user manual.

Polti have many models. All question need 'make model (what it is)' as the first 3 words in every question. Otherwise it is a but of a guess.

If it is getting hot, then it should be producing steam. There can only be on reason and that is that something is blocked with limescale. Has it ever been descaled?

https://www.fixya.com/support/r26134544-cleaning_laundry_iron

If it the type that has a hot flat iron and a hose to a steam generator tank, then it is possible that the element has failed. It is worth descaling that unit as well just in case there is a blockage down there. Add the descaling solution and turn it on for 5 minutes. Turn it off, leave 5 minutes and give it a shake every 5 minutes for 30 minutes. The descaling solution will only remove scale from places the solution touches.,

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Descaling a steamer, or anything else, in a hard water area must be done at regular intervals as mostly if it is left until it is needed it is too late for descaler and will either need to be dismantled and cleaned manually or thrown out.

In a hard water area it is preferable to use distilled water in steamers though deionized or boiled water would help slow the rate of scaling. Clean rainwater can be used and if you have an old-fashioned fridge/freezer you could use the meltwater from the deicing process.
As you know, water boils at 212 degrees F. Scale forms at 140 degrees and upwards and in hard water areas scale can form at a surprising rate...

We had this problem whilst still in warranty. Without question they sent a new iron. We have only used the di-ionised water in the new one making descaling much less painful

pour CLR in it this will descale the iron leave set for four hours or more

The best and cheapest way to descale irons,steamers, etc. is to use white vinegar, mixed 1 cup to a quart of water. Pour in the iron and allow to steam. The vinegar will dissolve the calcium, which is the blocking scale. Do this a few times toensure that the holes are clear and operating correctly. For the last rinse, put a little lemon into plain water and allow to steam. This gets rid of any vinegar smell.

No, there is special descaling fluid on the market just for that purpose. Make sure you get the correct fluid and handle it with care. These fluids are corrosive and poisonous. Read the instructions carefully.

Did you get the machine to work?

For Nespresso C250, you can look up Krups 554 or 580 and I found this manual http://safemanuals.com/user-guide-instructions-owner-manual/KRUPS/NESPRESSO-PROGRAMATIC-554-_E for download. I'm pretty sure this is the one!

have you tried fizzy cola?