Problem:
Conditionally update field value dependent on other field value using PHP

Solution:
User was using the wrong custom field slug due to that the value was not fetched within the Toolset form's hook cred_save_data.

You can find proposed solution in this case with the following reply:
=> https://toolset.com/forums/topic/conditionally-update-field-value-dependent-on-other-field-value-using-php/#post-2069753

Relevant Documentation:

Problem:

The issue here was that the user was getting a blank screen on the front.

Solution:

In this user's case they were getting the fatal error below when the wordpress debugging option was enabled.

[25-May-2021 14:55:10 UTC] PHP Fatal error:  Allowed memory size of 268435456 bytes exhausted (tried to allocate 20480 bytes) 

In a case like this all that is needed is to increase the wordpress allocated memory and the issue should be resolved.

To increase the wordpress memory please follow the instructions in the link below.
https://www.siteground.com/kb/increase-wp-memory-limit/#:~:text=To%20increase%20the%20WordPress%20Memory,on%20all%20shared%20hosting%20accounts.