I found a page for the SDK that matches my version of Sage 50 (2020.0) 

https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=101012&sliceId=1&noCount=true&isLoadPublishedVer=&docType=kc&docTypeID=DT_DOWNLOAD_1&stateId=24250&cmd=displayKC&dialogID=1232903&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl&openedFromSearchResults=true

However the link to download doesn't work. It opens to a 404 error:

404 - File or directory not found

The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.

How can I get the old SDK to test some DEV ideas?

It worked for me.

Hi Mark Crosby & Richard S. Ridings, 

Thanks for reaching out about this! I've let the Sage 50 Canada support team know about the article. Tested the download and I'm getting the 404 error whether logged in to the Sage Knowledgebase or not, so surprised that it worked for one of you. Will update you with any news.

Warm Regards.
Erzsi

Sorry, I didn't read the message carefully enough.  I didn't realise it was the actual download link that went 404, I thought it was the article itself.  Likely the article will now be removed as well as the file.

Mark, if the file doesn't surface, contact me off forum through my profile.  I think I have a copy of what you are looking for.

Hello Erzsi,

Are there any updates on where to get access to the Sage50 Canada SDK ? I'm still getting a 404 error and need to download it ASAP!

Thank you!

Niv

Hi NAbec, 

Currently only the 2023 version of the SDK is supported and can be downloaded here. The 2022 version was supported until March 31, 2023 as per the obsolescence policy here.

Looks like the 2022 SDK article for this hasn't yet been archived by the team but the download has already been pulled. This is the same for versions prior.

Sorry for this news. 

Warm Regards, 
Erzsi 

Hi NAbec, 

Currently only the 2023 version of the SDK is supported and can be downloaded here. The 2022 version was supported until March 31, 2023 as per the obsolescence policy here.

Looks like the 2022 SDK article for this hasn't yet been archived by the team but the download has already been pulled. This is the same for versions prior.

Sorry for this news. 

Warm Regards, 
Erzsi 

Hi Erzsi,

That URL is now showing as 'not available for all users'.   But no indication as to what the criteria are.    I'd like the new SDK to help support a client and their custom timesheet software developer.   

Without the 2025.0 SDK they will be stuck at Version 2024.2