I can't find my bitcoin address i am using electrum. First, I had a bitcoin address and I used it once to receive BTCs and then it changed. but new address is invalid.
i tired so many times. i checked all the options. but it was not OK.
what shall i do?
thank you
TL;DR: select Show Addresses item from the View menu. Then click the Addresses tab.




  First, I had a bitcoin address ...


A Hierarchical Deterministic (HD) wallet has many addresses.


  ... and I used it once to receive BTCs and then it changed.


That is normal, for privacy reasons, an HD wallet will generate a new receive address for each transaction in which you will receive BTCs.


  I can't find my bitcoin address


Look under the "Addresses" tab



(from a beginners guide)


  It will be hidden by default. To reveal it, select Show Addresses item from the View menu. 





  i checked according awebanalysis.com/en/bitcoin-address-validate 


I don't know that site but maybe you mis-typed an address or that site doesn't know about the type of address your wallet is using. Some online sites are not up-to-date with the latest Bitcoin features (e.g. Bech32 type addresses that start bc1...). Try another, for example http://lenschulwitz.com/base58