We have a site that shows this error any time anything in the maintenance routine runs, for each step in the routine.
ExecuteReader requires an open and available Connection. The connection's current state is closed

I put in code to log the open connections before it runs and it displays one open connection, as it always does in admin system reports.
I have looked through the code for ExecuteReader in custom code and all custom code uses NHibernate.
I looked in Sql Server settings, comparing all the properties with another database and they were the same.
Have you seen this before? Can you give any help? All the Google results I find refer to custom sql using sql data commands, etc, not nHibernate.
Thanks

I think the issue is in deleting the page views.
I constructed sql scripts to run the MaintainUsers routine on these two sites.
On the first one, they had > 1,000,000 anonymous users going back to 2001. The sql script to delete pageviews ran around 20 minutes then stopped because transaction log was full. Then after 15 minutes it stopped again.
The second site had 223,000 anonymous users and the script to delete page views stopped twice because transaction log was full. After the second time, I checked and there were still 18,000,000 entries in the page views table.
I finally just had to truncate the table to get things to finish up.
I think this is probably because of bots. They are more and more affecting our sites- enough that we have had to start using under attack mode on ClouldFlare at times.
Have you had issues on the sites you host?

There is a free CloudFlare account that has the basics and I believe it has the under attack option with it.
Sucuri also has bot protection features and it starts at 9.99 a month.