Is there compatibility between MATLAB update versions for protected models in R2019b through R2021a?

I created a protected model in R2019b Update 9 and I opened and ran it in R2019b. However, I got the following error message.

One or more global variables used by protected model E:\TEST\TEST_IP_Model.slxp are
incompatible with the variables that existed when the protected model was created.
This protected model uses global variable(s): 'TEST_bus'.

Answer 1

[MathWorks Support Team]

We would expect protected models to work in the same release that they were created, independently of the update version. However, this is not true for some releases.

This behavior was indirectly introduced as a side-effect of the fix for Bug Report 2429203 (that is why it appears in all the updates/releases where Bug Report 2429203 was implemented). 

The following table summarizes the affected releases and update versions:

Models that are Protected in    |   Cannot be used in 
--------------------------------|---------------------------------------------
R2019b Update 9 and later       |   R2019b Update 8 and before
R2020a Update 7 and later       |   R2020a Update 6 and before
R2020b Update 6 and later       |   R2020b Update 5 and before
R2021a and R2021a Update1       |   R2021a Update2 to R2021a Update 7  
R2021a Update 2 and later       |   R2021a and R2021a Update 1   

For example, between update versions in R2019b, if you protect your model in R2019b Update 9, you will only be able to use it in R2019b Update 9 and later. If you protect your model in R2019b Update 8 and before, it can be used in R2019b Update 8 and before.