You are impacted by the Salesforce Guest User access and permission changes that have been completely enforced with Spring 21.
Check out a few community posts about the matter. You can start with this one:
Please know that Salesforce has removed the ability for guest users to edit records completely. So if your contacts had any ability to edit records using the UID link - this will have been removed by Salesforce. Skuid has no way of restoring that access. You will need to address that with Salesforce.
Look at that link above, and explore some other posts about Guest User access.
