Can't access iDRAC9 Web UI

I have a PowerEdge R640 server. I was previously able to access the Web UI, but now I just get a never ending spinning wheel. I can ping the IP & SSH into it, but I'm not sure what to do once I'm in. Any suggestions on how I can access the UI again?

First, did you try another browser or to clear your cache.

If yes, then please unplug the server completely to have the iDRAC reset and after please do firmware update if some update are available to it.

You can jump to the version 4.0.0.0 if you can, it add stability to the iDRAC.

iDRAC with Lifecycle Controller, 4.00.00.00 Fixes & Enhancements Fixes - Stability and performance improvements

Thanks for the help everyone. I had tired Chrome, Firefox & IE with & without private browsing with no luck. I just found this link. I held down the "i" button on the front panel for 20 sec. and iDRAC reset itself without powering down the server or losing its configuration.

An R640 is not that old, and certainly should work with modern browsers - the old java version requirements of older DRACs isn't yet a thing for DRAC9.

If you have physical access to the box (or competent smart-hands) then try draining the flea power and no I'm not making that name up.

The usual process is

1. Safely power off using the OS.
2. Then removed every power cable from the host (multiple PSUs are possible) and to also unpower any direct-attached components like disk shelves or PCIE expanders or any USB or serial device with its own power supply. Ethernet switches are fine to ignore but console cables should be disconnected.
3. With the host completely stone dead, press and hold the host's front panel power button down for at least 30 seconds, then release. Make sure you get the correct host - in a rack of identical hardware its easy to get the wrong box.
4. Reconnect all device cables.
5. Reconnect all power cables. You may have to start the host with a brief press of the power button.

Note I've never done this on 48V DC-powered kit - on these the power leads are generally hard wired to the PSU. Be extra careful if you have DC power.

It may sound ridiculous, but this has been a "last resort" option that can fix the weirdest problems which have survived complete reboots of the host.