mex file issue with version 2019b

I just upadate to 2019b and getting errors using psych toolbox adn calls such as KbWait. the errors are below:

In place of the expected mex file this placeholder file was executed:

Screen

This mex file seems to be missing or inaccessible on your Matlab path or it is dysfunctional:

Screen.mexw64

Hmm. I cannot find the file on your Matlab path?!?

One reason could be that your Matlab path is wrong or not up to date

for the current Psychtoolbox. You may want to run SetupPsychtoolbox to

fix possible path problems.

Error using AssertMex (line 190)

Missing or dysfunctional Psychtoolbox Mex file for this operating system. Read the help text above carefully!!

Error in Screen (line 158)

AssertMex('Screen.m');

Error in KbCheck (line 286)

[keyIsDown,secs, keyCode]= Screen('GetMouseHelper', -1, [], deviceNumber);

Error in KbWait (line 129)

[isDown, secs, keyCode, deltaSecs] = KbCheck(deviceNumber);

How do I fix this issue?

thanks in advanced.