We have worked with Yodlee to resolve the issue. It was identified as a fault in their refresh system. All accounts should refresh okay now.
Posted Apr 20, 2019 - 09:42 BST
Update
We are continuing to investigate this issue.
Posted Apr 19, 2019 - 16:38 BST
Investigating
We are having issues with Plum accounts fetching data. This could also affect new and old users trying to (re)link their bank accounts and are finding themselves stuck at "securely linking". Do not worry, this does not affect your ability to manually deposit/withdraw.