Question: 

My custom theme cannot get the less file of Bss_SimpleDetailGroupedProduct. How can I fix it?


Answer: 

- The Cause: As MSG - Ninth theme doesn’t follow Magento 2 Less compiler standard, if your extension is using _module.less that follows Magento 2 Coding Standard, this theme cannot get the _module.less file

- The solution:

Step 1:

Go to the folder: magento/app/design/frontend/Mgs/ninth/web/css/third-party-extension (if there is no third-party-extension folder, we suggest you should create one to manage code easier)

Then please add bss_sdgp.less file  to the folder.


Step 2:
Go to the file: magento/app/design/frontend/Mgs/ninth/web/css.theme.less, add code:  @import 'third-party_extension/bss_sdgp.less'; to import bss_sdgp.less  file into the theme.


Step 3: 

Deploy the site, so the site has the new CSS. 


Note: If your less file using Magento 2 Standard Media Query, you may encounter errors. We recommend using Standard Css Media instead. Ex:
Your less file with Magento 2 Media Querry
.media-width(@extremum, @break) when (@extremum = 'max') and (@break = @screen__m) {}

Now convert to Css Query
@media screen and (max-width: 600px) {}


Could you please check and contact us is there is any concern?