I too have again been experiencing problems with Alliant. My problem is with Alliant Credit Union and is CC-505. @Quicken Anja, I expect @Longtimeuserr is referring to the ongoing problems discussed in other threads. In addition to the discussion that this thread was split from, here are two more:
Download from Alliant Credit Union not working — Quicken
Continual CC-505 and CC-503 errors with Alliant Credit Union — Quicken
As I recall, @SeattleSummer76 chased this problem until Alliant finally admitted that due to capacity limitations they turned off Quicken access to Alliant in the morning hours. My guess is that Alliant has again started this practice. If this is correct then, there are two courses of action – live with this sporadic problem or change your credit union. My decision was to live with the problem, but I have minimized the issue by opening an account at another credit union where the majority of my transactions now occur.