Litecoin address starting with ltc my litecoin wallet (shared 2 of 2) on electrum-ltc generated an address to receive LTC. I transfered some LTC to that address and tried to check in block explorer. Unfortunately got such message:
Sorry, 'ltc1qy4rwhdkujk35ga26774gqmng67kgggtqnsx9vp0xgzp3wz3yjkhqashszw' is not a valid LTC address, wallet name, transaction or block.

Is it something wrong with my LTC address? Electrum-ltc v 3.1.3.1. From what I know it is Bech32 Segwit address.
Your address is in the native-segwit format (also known as bech32).

It's an entirely new address encoding scheme for segwit addresses, and many exchanges, explorers, and wallets don't currently support it. 

If you are unable to send coins to it due to the sender not supporting these addresses, you will need to set up a new Electrum wallet, and during the setup process, use P2SH-P2PKH addresses, which will start with M. 

If the sender still does not accept the address, you can convert it to one starting with 3 using https://litecoin-project.github.io/p2sh-convert/.

https://insight.litecore.io will accept addresses starting with M for balance checks, and show outputs to the ltc1 addresses, but it will not have an address page for the latter.