Browser / Version: Firefox Mobile 61.0
Operating System: Android 7.0
Tested Another Browser: Yes
Problem type: Something else
Description: Could not install as a web app
Steps to Reproduce:
In Chrome 66, this website could be added properly to the home screen. I suspect tbat there might be a problem in the website's web app manifest.
_From webcompat.com with 鉂わ笍_
Thanks for the report @reinhart1010.
On Firefox I was able to add a shortcut (Settings>Page>Add Page Shortcut) and it's available in Home screen.
On Chrome I added it to Home screen too (Settings>Add to Home screen).
Are you referring to something else?
Tested with:
Browser / Version: Firefox Nightly 62.0a1 (2018-05-07)
Operating System: Google Pixel (Android 8.1.0) - 1080 x 1920 pixels (~441 ppi pixel density), Samsung Galaxy S6 (Android 7.0) - Resolution 1440 x 2560 pixels (~577 ppi pixel density)
Here, the "add to Home Screen" feature meant is to install as a Progressive Web App. In Chrome, opening the app icon on home screen will treat the website as a full-screen webapp.
I see, thanks @reinhart1010 for clarification.
It appears that since the site is not fully secure, Firefox does not support PWA.

Link to manifest:
<link rel="manifest" href="/manifest.json">
Moving to Needsdiagnosis for further investigation.
One image is I guess by mistake with an http link instead of https.
.css-g7nhgw {
background-repeat: no-repeat;
width: 36px;
height: 36px;
background-size: contain;
display: block;
position: relative;
top: 5px;
left: calc(50% - 18px);
background-image: url(http://ecs7.tokopedia.net/img/cache/100-square/attachment/2018/4/25/1032/1032_0f718186-39a1-4074-85f1-76392b4fb61e.png);
}
They just need to fix this.
Thanks @softvision-oana-arbuzov for finding out the cause.
Pushing to needscontact
The contact page.
https://www.tokopedia.com/contact-us?nref=footerhome#step1
@karlcow The help page does not include sections for technical issues.

Sections Mentioned: Accounts, Transactions, Product Categories (e.g. prepaid phone top-up and product sales), Product Delivery, Promotions, TokoCash and TokoPoints (e-money and points system), Flash Sale, Usage Abuse, as well as Content Feeds.
Here, the "Content Feeds" section might seem the most appropriate, while this is only relevant to issues with Content (or Product) Feeds instead of other technical issues.
Alternatively, Tokopedia is available on Twitter as @tokopedia, as well as @TokopediaCare for handling issues with users. I might mention both in contacting them.
Okay I have contacted them via Twitter.
First responded by TokopediaCare
Finally, this issue is fixed. Tested on Nightly 62, Android 7.0.

Closing this as the first fixed webcompat issue in Indonesian websites. 馃帀
Congratulations @reinhart1010
Most helpful comment
Closing this as the first fixed webcompat issue in Indonesian websites. 馃帀