Waalaikumsalam. Pertama2, apakah anda telah mengikuti tutorial di youtube kami? https://youtu.be/JEgJzh6IqUk

Kalau boleh tahu, anda memakai Ubuntu versi yg ke berapa? Kemungkinan pertama, Ubuntu anda perlu diupgrade ke versi yg lebih baru, yaitu versi 20.04 LTS. 

Pak Ari. Pada Turn windows feature on or off di PC saya pilihannya hanya windows subsystem for linux (beta), sehingga ketika saya masuk lagi ke store dan pilih get ubuntu 20.04 LTS tertulis something happened on our end. Gimana nih pak, belum berhasil install

@mashafii70 Silahkan untuk mecoba langkah ini Pak

https://windowsreport.com/try-that-again-something-happened/

Assalamualaikum wr wb. Maaf saya ada permasalahan instal ubuntu 20 nya di windows, Pada waktu

sudo add-apt-repository  http://dl.openfoam.org/ubuntu 

muncul eror 
W: GPG error:  http://dl.openfoam.org/ubuntu  focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6C0DAC728B29D817
E: The repository 'http://dl.openfoam.org/ubuntu focal InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Lalu step selanjutnya 
sudo apt-get update > juga eror
Err:3  http://dl.openfoam.org/ubuntu  focal InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6C0DAC728B29D817
Reading package lists... Done
W: GPG error:  http://dl.openfoam.org/ubuntu  focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6C0DAC728B29D817
E: The repository 'http://dl.openfoam.org/ubuntu focal InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details. 
Lalu pada saat instal openfoam >
sudo apt-get install openfoam8
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package openfoam8

Mohon arahan dan sarannya, terimakasih. 

@syarifah Waalaikumsalam. Coba ikuti langkah berikut ini

1. Restart komputer
2. Buka program Ubuntu
3. Ketik di terminal Ubuntu atau bisa juga copas code ini

sudo sh -c "wget -O -  http://dl.openfoam.org/gpg.key  | apt-key add -"
sudo add-apt-repository  http://dl.openfoam.org/ubuntu 
sudo apt-get update
sudo apt-get install openfoam8

@ariham Terimakasih Pak Ari. Akan saya coba terlebih dahulu.