Hi Link,
As I understand that, your SharePoint site has been upgraded to 15.0.0.4455, however, the Office 365 portal page remains with old style, is it right?
The issue could be related to the service upgrade at back-end side. If you have this issue on all wave 14 workflows? List workflow, reusable workflow, site workflow?
Also, please confirm if you can create a brand new workflow in SharePoint designer 2013 successfully.
I have also sent a private message to you about this issue, and you can check private messages with the following steps:
• Go to the Your details section on the right side of the community site.
• Click Private messages.
• Click the subject title of the response to read the message.
• You can reply by using the form in this display.
• Click Submit Reply.
Thanks,
Allen Qiu