When I charge my power bank, all the lights are blinking but not charging, is it broken already?

That's a strange behaviour. See power bank user manual to understand normal behaviour. When you charge your power bank, the LED light bulbs should flash/blink and indicate charge progression up to 100%.

Why power bank is not charging

It is possible that the indicative charging lights are working normally but without a corresponding capacity input for the power bank's rated mAh.  It is likely that your power bank is broken or is a fake. Either conditions may imply bad internal control circuit resulting in failure to charge.

Fake power banks look deceptively good and cheap. But you soon realise you’ve been swindled and you really get to know how costly they are when they don’t work or if they explode. But there are few things to check in order to avoid fake power banks.

How long have you had it for? If new and still in warranty, best to return it. Even if out of warranty, still take it back if you can and seek explanation from the seller. Otherwise email the manufacturer/seller and see what they say.

Best of luck.

Solar Power Bank: Buy Universal Power Bank Chargers Online | HetoGrow