@Dawn KassubeI am looking into this question for you.
I have now gotten some feedback on your question.
for the HTML that you provided - the one note is to make sure there is a space between the hyperlink and the target="_blank"
HTML:<a href="https://teams.microsoft.com/l/file/E7A97489-5FBE-43DD-80FC-01519D7EEE99?tenantId=ce56fae6-055d-4c9f-b6c9-9d341506a491&fileType=pdf&objectUrl=https%3A%2F%2Fqbe.sharepoint.com%2Fsites%2FITBMCostModelandExpenseArticulation%2FShared%20Documents%2FApptio%20Training%2FCost%20Model%20Diagram.pdf&baseUrl=https%3A%2F%2Fqbe.sharepoint.com%2Fsites%2FITBMCostModelandExpenseArticulation&serviceName=teams&threadId=19:378f280e462449c4a24f45910b88f515@thread.skype&groupId=543a48bc-d4c4-421b-a808-51c1e7bca465" target="_blank"><button type="button">Review Cost Model Allocation Diagram</button></a>there is also another option of adding a HTML box which can be the hyperlink you are looking for:
https://teams.microsoft.com/l/file/E7A97489-5FBE-43DD-80FC-01519D7EEE99?tenantId=ce56fae6-055d-4c9f-b6c9-9d341506a491&fileType=pdf&objectUrl=https%3A%2F%2Fqbe.sharepoint.com%2Fsites%2FITBMCostModelandExpenseArticulation%2FShared%20Documents%2FApptio%20Training%2FCost%20Model%20Diagram.pdf&baseUrl=https%3A%2F%2Fqbe.sharepoint.com%2Fsites%2FITBMCostModelandExpenseArticulation&serviceName=teams&threadId=19:378f280e462449c4a24f45910b88f515@thread.skype&groupId=543a48bc-d4c4-421b-a808-51c1e7bca465"
target="_blank">Review Cost Model Allocation Diagram</a>that should then create a hyperlink

Please let me know if either of those options work for you. If they don't, I can reach out again for more help with this.
#CostingStandard(CT-Foundation)