i'm unable to press the ''send'' button
Check the wallet name in the status bar, 2fa wallets have [2fa] tag after it.
Because that balance isn't enough to pay Trusted Coin's initial payment for your next 20/100 transactions; plus the fee and the amount to be sent.
More info: trustedcoin.com - FAQs | Scroll up to know more about Trusted Coin which is Electrum's 2fa service provider.
Or are you using the mobile version and it's not a 2fa wallet?
In mobile, "Send" isn't a button but a 'tab', in that tab, you'll have to click "Pay" in order to send the transaction.