I am having same problem on two completely separate blogs, both hosted by Yahoo. The blogs have been running for over a year, with no problems. They both started this failure to update plugins within the last couple of weeks. I also get the error Download failed. error:0D0890A1:asn1 encoding routines:ASN1_verify:unknown message digest algorithm
Yahoo claims they haven’t changed anything. The problems does seem to coincide with the update of WordPress to ver. 4.3. I tried disabling all my plugins and then updating them individually and as a group, both while disabled and after enabling them one at a time. No difference. Same error. Tried to reinstall WordPress, and got the same error.
I have not tried to install anything manually, because I am not sufficiently sophisticated to be able to do that. Besides, even if I could learn how, I don’t want to be manually installing updates for all my plugins, that is the reason I use the darn dashboard. I also have no idea how to code.
Alan