Does the client know the position of any of the words of the seed phrase or does he not have any idea what goes where? It would certainly speed things up if he knew, at least, some of the words. It's good that you have the funded address. I still think that BTCrecover is the way to go here. You can take a look at
this guide that concerns the recovery of seed words.
If nothing else works, you could use a trusted paid service. Dave's wallet recovery services have been around for years, and he knows what he is doing. If you and your friend can't manage yourselves, contact Dave.
https://bitcointalksearch.org/topic/bitcoin-wallet-recovery-services-for-forgotten-wallet-password-240779https://www.walletrecoveryservices.com/
Someone who knows much more than me about these things estimated a long time ago that it would take 200 years to bruteforce the order of a 24-word seed. Yours has 12 words, but it would still be a difficult task. And there have been advancements in computer tech since 2017. Anyways, good luck!
So, you have 24 words.
That means that you have 24 possibilities for the word in position number 1.
If you try each of those words in position number 1, that leaves 23 words to try in position number 2.
Try the first word, with each of the other 23 in the second position, then try the second word with each of the other 23 in the second position, then the third word with each of the other 23 in the second position and so on.
When you've done that, you'll have tried:24 X 23 = 552 different possibilities.
Each of those 552 possibilities will have 22 remaining words that you can try in the third position.
So that's:
552 X 22 = 12144 possible combinations of 3 out of the 24 words.
(Notice that's the same as 24 X 23 X 22 = 12144)
Then for each of those 12144 possibilities will have 21 remaining words that you can try in the third position
That's:
12144 X 21 = 255024 possible combinations of 4 out of the 24 words.
(Notice that's the same as 24 X 23 X 22 X 21= 255024)
Perhaps you can see now that as we continue, by the time you try all the 24 word combinations of 24 words, the pattern will repeat all the way to:
24 X 23 X 22 X 21 X 20 X 19 X 18 X 17 X 16 X 15 X 14 X 13 X 12 X 11 X 10 X 9 X 8 X 7 X 6 X 5 X 4 X 3 X 2 X 1 = ?
In maths that pattern is called a "factorial" and is represented as:
24!
If you do that multiplication, you'll find that the total number of combinations you'll have to try will be:
620448401733239439360000
That's about 6.2 X 1023.
Lets assume that you have enough computing power to try 100 trillion combinations per second.
620448401733239439360000 combinations / 100000000000000 combinatins per second = 6204484017 seconds.
Since there are 60 seconds in a minute, that is:
6204484017 seconds / 60 seconds per minute = 103408066 minutes.
There are 60 minutes in an hour, so:
103408066 minutes / 60 minutes per hour = 1723467 hours.
There are 24 hours in a day...
1723467 hours / 24 hours per day = 71811 days.
There are about 365.25 days per year...
71811 days / 365.25 days per year = 196.6 years.
If you actually had the ability to try 100 trillion combinations per second, then it's going to take you nearly 200 years of trying non-stop 24 hours a day to try all the combinations.
If the number of attempts you can make per second is less, then obviously it's going to take you longer than that.
The only way you are going to be able to find the right combination in your lifetime is if you already have some of the words in the right order, or if you can remember what order some of the words belong in. Knowing for certain the position of just 1 word reduces the effort required by a factor of 24. Knowing for certain the position of just 2 words reduces the effort by a factor of 552.
Using our "100 trillion combinations per second" example, knowing for certain the position of 1 word reduces the time required to try all possibilities from 196.6 years to:
196.6 / 24 = 8.2 years.
Knowing for certain the position of 2 words reduces the time required to try all possibilities to:
196.6 / 552 = 0.36 years (about 4.3 months) 
