Help recovering history/bitcoins from Electrum wallet

Start by reviewing the reported recovery behavior in Electrum 3.0.6 and 1.9.7, then investigate the 1.7.2 release-note guidance about visiting a full server. Check the gap-limit, server, and command-line recovery paths described in the report. Done means explaining why the wallet is empty or documenting a reliable way to restore its balance and history.

n 2013 or 2014, I set up a standard Electrum wallet (downloaded a version of 1.7 from the electrum.org website on Windows with Linux). Kept a record of my password and the 12-word seed. Created only one Electrum wallet so I know it’s the only password and seed.

Haven’t touched the account in years but there was some activity in it around the time it was created.

Recently downloaded Electrum 3.0.6 and entered my password. This opened a wallet that contains the correct 12-word seed. But the wallet pops up empty. No BTC, no history.

If it’s relevant, the wallet was originally created on a Windows computer but I am now using a Macbook Pro 15 (High Sierra 10.13.3).

Here’s what I tried so far:

• Opening the wallet with the password AND recovering from seed on BOTH version 3.0.6 as well as version 1.9.7 (the oldest version I could now download from electrum.org).
• Increasing the gap limit to 120.
• Started trying to plug addresses into blockexplorer.info. Tons of addresses to try and I’ve gotten nowhere so far though will keep trying.
• Changing servers (both on 1.9.7 and 3.0.6), both with and without checking the automatic box. Used SSL and no proxy. On 3.0.6 also tried without SSL and with SOCKS5.
• Can’t seem to get the command line working in Electrum (Terminal works just fine and I can open Electrum from it but I can’t seem to access the Electrum command line). If I could figure this out I’d try to rescan.
• Found this which sounds promising but have absolutely no idea what it means:
  “It seems that the RELEASE-NOTES from version 1.7.2 says
  * Due to an internal format change, your history may be pruned when
  you open your wallet for the first time after upgrading to 1.7.2. If
  this is the case, please visit a full server to restore your full history. You will only need to do that once.”
  Anyone know what is meant by a “full server” in this context? Could anyone translate this into English for a newbie or suggest something I haven’t tried? Many thanks.