To vote on issues you must be logged into Jira.
There are two views in Jira, you can vote in either view
How to disable the new Jira view
Click on 'See old view link' or click on your user icon then settings then in Jira labs section toggle the slider off
There may be a purple Atlassian message that sites on top of of the page that you may need to dismiss prior to being able to see the option to the old view of Jira.
How to vote via the new issue view
In the new issue view, click on the thumbs up icon
How to vote via the old issue view
In the old issue view, click on the 'Vote for this issue' link
Don't have Jira?
If you have logged into our Portal for support you have access to Jira features as a Jira user. Just log in to our portal and then navigate from there to the issue that your ticket has been escalated to.
There is a known issue JSDSERVER-1367
That is a redirect loop that keeps directing you back to the Portal rather than following the link to a Jira Issue. Please go and vote on the above issue to let Atlassian know you are having this problem. Currently, there is no known workaround.