Unable to start SSRS sevice after upgrading SQL Server instance

I recently spent quite a few time trying to figure out why my SSRS service fails to start after performing upgrade from SQL Server 2012 to SQL Server 2016. Service was failing to start with quite generic error “System error 5 has occurred. Access is denied” which is a bit to broad, but after a while I looked into instance bin directory which contains log file where I seen some error indicating that configuration file is garbled somehow. At this point I revert to reinstall once again solution, and this time I noticed warning which I probably missed during initial instance upgrade attempt:

TITLE: Microsoft SQL Server 2016 Setup

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The following error has occurred:

Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index

For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft%20SQL%20Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=13.0.1711.0&EvtType=0x35C10BED%25400xF538E98B

I proceed with upgrade I seen exactly the same problem – I can’t start SSRS service after upgrade completion. This warning essentially lead me to the thread on TechNet containing right solution. It seems that upgrade process somehow can’t handle SSL bindings for SSRS service or handles them differently (produces malformed XML configuration for them?) and what you need to do is remove SSL bindings for SSRS in Reporting Services Configuration Manager (see screenshot below).

Just to save some time which may be wasted on troubleshooting just remove your SSL bindings (I did it for Web Service URL & Web Portal URL) before starting upgade of your instance. You may add these bindings back after upgrade.