Thanks for your advice guys, for sure it will be helpful!!

PROBLEM SOLVED 

After trying a lot of different alternatives, the solution was to type a single space just at the beginning of the extension. All the other words, symbols, and numbers were exactly the same as I had written them down.  So the problem wasn't a different keyboard layout. The problem was that I didn't pay attention when I created the wallet to remark that there was space between the first 12 words and the extension.

I hope this can help in future to other people.

Thanks a lot guys for your help and cooperation, I appreciate it so much, good luck!

Ok guys, thanks for your answers!
 I'm new on the forum so I don't know if this is the correct way to reply to all of you.

BlackHatCoiner: I've tried entering the whole seed phrase, exactly as I wrote it down in the paper when I created it. When I created it, I added 15 more words separated with spaces, and in the end I added the numbers and symbols all together. So the final part of the phrase was : 79&%;@:03!+# (just an example).  So let me know if I understand what you say, Should I type the numbers and symbols separated with spaces between them?

Charles Tim: The balance is 0. So Electrum recognizes the first 12 words, then I click the option to extend the phrase, I type the extension in the next screen, and then the wallet shows no transaction nor btc.

nc50lc: Yes, I click the option to extend the phrase, so I don't type all together in the first screen of the seed. I'm new in using Electrum so, what does it mean that I typed wrong the BIP39 phrase, and the key pairs?

o_e_l_e_o: I've done exactly what you said, but the problem persist. Do you also suggest me to introduce spaces between every number and symbol?

Coin-keeper: It could be a possibility. I use the same keyboard, but when I use Ubuntu, the characters are not in the same position of the characters on Windows when I type them.

Hello everyone,

The last year I created three wallets, with Electrum, using Ubuntu installed on a USB. I only saved the files on the USB, Huge mistake

This year I tried to access to the wallets again, but the USB isn't working, so I had to use the seed phrase to recover them.

For two of the wallets, I didn't have any problem using the seed phrases, they worked fine and I can use the wallets again.

But for the last one, when I created it the last year, I used the option available in Electrum to extend the phrase manually, when you install the wallet, so in the next step you have an available space where you can continue extending the 12 word phrase. I extended it with 15 more words written by me, 4 numbers and 8 random keyboard characters like:   ')#%&/*@_! .  

So in total, the seed phrase was made of 27 words,  4 numbers and 8 symbols. The wallet was succesfully installed, and I made transactions with it. I had written down the seed phrase in a paper, but when I enter it in Electrum right now, using Windows 10 and the last version of Electrum, it doesn't work, no wallet shows up.


Does anyone has any suggestion of a possible solution?  


Thanks for your time,