SharePoint site with K2 Form Viewer web part.
After switching the account in SP Online, the K2 account of the previous user stays active.
Issue has been fixed in 4.7 March 2018 CU FP7.https://help.k2.com/kb002355
If you have the fix applied but the issue is still persisting, make sure of the following:
Please use K2 Form Viewer to select the required Form from the list instead of adding the form URL into the web part properties manually, so the form URL should look like the following example: https://[TenantName]-[AppID].sharepoint.com/sites/[AppcatalogSiteName]/K2FiveforSharePoint/Pages/For...
Selecting the Form/View from the list below resolves the issue