I would generally first consult this source... https://open.concur.com/?data-center=pscc
specific to your question I don't see the system was down recently, so my best suggestion would be to consult within your company reference person managing the Concur system who eventually could escalate to Concur directly. It could be even a reasons of clearing the browsing history from your computer or general slowing down of your system network.
@zk7dm77 for issues regarding the loss of the Expense tab, log into SAP Concur and check the Company Notes section. Usually that is where you can find contact information for help with issues. If there isn't contact information there, work with your direct manager. Normally I would look up someone in your site to contact, but for some reason I cannot access your site.