QB Issue Resolution:
I’ll guess that the message is complaining about the !SPL row in your file.
It should not have a TRNSID field, but instead a SPLID field as seen in the attachment.
If you open the IIF file in Excel, what fields are included on the !SPL row?
Resolution for Issue '“[ERROR] TRNSID is not a valid column name for record GENERAL_JOURNALSPL.  ” What changed with the 2019 import and how can we fix so we are able to import?' available: Yes (Solved).
Source: Intuit Community forum.
“[ERROR] TRNSID is not a valid column name for record GENERAL_JOURNALSPL.  ” What changed with the 2019 import and how can we fix so we are able to import?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.Support for GENERALJOURNALSPL
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Error Recovery for GENERALJOURNALSPL [Canada]
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