I am here to tell you that you can have multiple applications, as long as only one is brought to completion with enrollment. I currently have three that I am actively pursuing. Whichever one gets me to the end is still being contested.
Application #1 - Online and completed; however, enrollment had me mistakenly identified as 10 people, which looks like it has been fixed! However, now that there is only one of me on that application, the process stops at "Set premium tax credit". The amount of my tax credit to use and my choice of ways to apply it is a blank space, and the top of the page says there is an error in getting my tax credit information, so clicking on "Use this amount" does nothing.
Application #2 - Online (had to skip the verification of identity) and I can get to inputting my income information but the next page says "Sorry, our system is down. Try again in 30 minutes". That was the message for the last five hours.
Application #3 - Phone application, otherwise known as paper application. It has to be processed and mailed to me by the USPS. Who knows when that will be - I've read that others are waiting weeks.
Every time they fix something, something else that wasn't broken....breaks.
Whomever is going to respond that I should clear my cache or clear my cookies or use a different browser or try in the early morning or late evening - it's all been tried. The results are the same.
I am actually excited every time I get further than the last time :-)