Hi Scott,
A helpful tool is built into the application which will walk the team through managing these permissions at a more granular level. Within the application, navigate to the help > advanced topic screen :
This will bring up the documentation where you will find a section labeled "managing permissions" :
Based on the issue description, if the permissions tied to your ID / data flow is updated to "write", everything runs successfully? This question is simply to ensure that the problem truly is around the "write" permissions within the application, rather than some outside factor. The error you mention is giving me pause :
Execution Error: Error executing http request 'while performing dataflow execution': 'null'
Matthew Kennedy