Missing stored procedure messages are in relation to Nintex databases not being updated properly. To ensure your databases are updated, run the following commands in the SharePoint Management Shell or Powershell with Add-PSSnapin Microsoft.SharePoint.PowerShell:

For Nintex Workflow Databases: 
NWAdmin.exe -o UpgradeDatabases

For Nintex Forms Databases: 
Install-NFService
Upgrade-NFService

Examples include but are not limited to: NWAdmin -o DetachDatabase - Could not find stored procedure 'GetExtIOSiteMapping' Publishing a Nintex Form - Could not find stored procedure 'NM_DeleteFormByContentTypeAndList' Publishing a Nintex Workflow - Server was unable to process request. ----> Cound not find stored procedure 'NM_DeleteFormByWorkflowBaseID'

These errors indicate that a stored procedure is not present in a database. Running the relevant commands updates/checks the database schema and should recreate the stored procedure.

NWAdmin -o UpgradeDatabases
UpgradeDatabases

Install-NFService
Install-NFService

Upgrade-NFService
Upgrade-NFService