I just got a Spark and it seems to link with the RC okay (I went through the linking process) but the drone won't do anything. I can't do anything with my phone because every time I connect to the Spark Wi-Fi it jumps back to household Wi-Fi after 3-4 seconds; I can't even get a firmware update it keeps telling me about. I do sometimes manage to get a few seconds of video before it disconnects. This happens over and over. Do I have to be out of range of any other Wi-Fi to be able to fly this? I also keep getting a message telling me that WLAN settings have to be changed and I should try connecting later. Technical support doesn't seem to have a clue.

May I know the model of your phone? Have you tried another one in dji recommended list? If you have the same issue with the device which is in the list, please export the data from black box for further analysis.
Besides, would you please help us confirm the firmware version for the device? Check the details on "About" page via APP when all are connected properly, it would be better if you can upload a screenshot here, thanks.
To export the data from black log, please download the Assistant 2 from DJI official Spark website page, install it then connect the drone to PC and run Assistant 2, you will get the file. Upload it to Dropbox and post the link here.