My MG 2520 printed and stoped the triangle light flashes.Changed ink

Check for a 5B00, 5B02 or similar family of waste ink errors and the early warning codes related to waste ink. When you change the ink carts, they always purge a small amount of ink to prepare the cartridge. If your waste ink pad is 95% full, for example, that cartridge change will very often trigger it, and what makes it hard is the WC NVRAM percentage can be high (80%), but the printer can survive 10 cart changes, sometimes less. There is no good way to determine when it dies with a hard stop due to waste ink. NONE!
NOTE: 8 blinks=waste ink pad is full.

See if WIC Reset Utility can be used to reset the counter if this is the case. If you cannot, the printer is effectively ewaste. The official Canon utilities WILL NOT RESET IT, and is known to not do it -- it's intentional. On these, its potentially a permanent flag if the printer is considered "disposable" and this is one of them. However, try the Canon reset tool known as V3800 if you want to give this a shot, but you will also need to put it in service mode first; it may somehow work.

This procedure may work for your model if the tools do not and it has service mode access. If it cannot be done, it's a permanent one-time flag that cannot be reset, even by Canon.

Canon, of course, doesn't warn you NOT TO CHANGE THE INK once you see the message (either clean/replace the pads or replace the printer; no more ink for that unit) for... obvious reasons. Seriously, if I had a Canon with the early warning I'd refill the set of ink I have while it works then let the counter hit 100%; worst case, I'm out $5-10 in bulk ink, not $40-50!

The reason I would refill my carts with this error is so if it trips after 5 cleaning cycles, the "most" I wasted was commodity bulk ink I can throw into a printer from Walmart I bought for $30 to consume the ink that should it die due to a WIC eror, it was $30 or less.

Now that said: On my perfectly good photo printer I wouldn't do this since it has the 5 color system (kind of hard to find a photo printer with the 5th color in a retail store), but a cheap cartrdge based (in case the carts fail and it lives on loger then expected) CMYK unit is completely fair game to kill with refill inks. But say that same photo printer had a Canon waste ink is nearly full error... Yep, you're drinking bulk ink for what little life you have left before the 5B02 code comes up.

If it's not a waste error, something is in the platen path or the ink carts are loose. Check for obstructions or damage, and make sure it isn't catastrophic -- if it's something like paper, removing it will probably solve the issue. The other issue I see is generally bad ink carts. Try another set and see if it still occurs; if it does, then you may have a bad carrier contract strip. Try cleaning it with alcohol, but if it doesn't work, it may physically fail.