I haven’t heard of this problem with security software warning about Electrum. Mind sharing the name of the software?
However, if you’re using the words from the Blockstack Browser to recover your BTC, it’s expected that you won’t see any BTC balance with Electrum. These instructions are specifically for recovering BTC from the older desktop Stacks Wallet, which was configured with either a hardware device like Ledger or Trezor, or 24-word Secret Key (as opposed to the Blockstack Browser’s 12-word keys).
If you’re trying to get BTC out of the wallet associated with your Blockstack ID / the Blockstack Browser, you can still use the Blockstack Browser itself for this purpose at the following address once you’ve authenticated: Blockstack Browser