I've investigated this:
Looks like Instagram has added another login step which happens after it is clear that the account is valid but technically the login is not complete yet.
This causes the username/password login to fail.
I was unable to fix this problem and I'm unsure if it even makes any sense to put more time into this as Instagram has changed their login process quite frequently in the past.
For now I've updated the plugin to show a dialog to the user which recommends trying again via cookie login and links the cookie login instructions to the user.
For all code changes mentioned in this post, the following information applies:
Bitte auf das nächste
CORE-Update warten!
Please wait for the next
CORE-Update!
Wartest du auf einen angekündigten Bugfix oder ein neues Feature?
Updates werden nicht immer sofort bereitgestellt!
Bitte lies unser Update FAQ! | Please read our Update FAQ!
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Are you waiting for recently announced changes to get released?
Updates to not necessarily get released immediately!
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-psp-