I was advised to ask here by one of the people from Shopify support.
I have uploaded ~700 items from Retail Edge to Shopify- though I have around 7000 that still need to be uploaded. I am unable to upload these unless I change their name on Retail Edge (delete it and re-type it up) or change their quantity on Shopify.
Any other ways to upload items or fix this problem are greatly appreciated! 
If your using an offplatforms integration with shopify you need to contact that other platforms support for issues with their software.
Unfortunately your description does not give enough information for someone to guess what the problem is unless they are intimately familiar with both platforms.
The sanest approach for cross platform migration to shopify is to get your product data in CSVs
https://help.shopify.com/en/manual/products/import-export/using-csv
Unless you need a constant platform to platform sync of data in which case if their integration is garbage you will need to build your own sync application or find a middleware provider if one exists.
If the other platform has a http api I can build a product fetch in mechanic.
If you need your own middleware and have a serious budget and you have the platforms development docs and then contact me directly by mail for services.
Please always provide context, examples: store url, theme name, post url(s) , or any further detail.
Contact Info in signature.
Good Hunting.