There's a new version of the HubSpot API

As of November 30, 2022, HubSpot API Keys are being deprecated and are no longer supported. Continued use of HubSpot API Keys is a security risk to your account and data. Your API Keys could be deactivated at any time after Nov. 30th, and we recommend that you migrate to Private Apps as soon as possible so you do not lose business-critical functionality.

How do I set multiple values for checkbox properties?

When setting multiple values for a checkox property, the values should be separated with a semicolon (;).
'value1;value2;value5'

When updating a record through the Contacts API, the property value should be a single string with all of the values separated by semicolons:

{
    "property": "property_name",
    "value": "value1;value3;value4"
},

 

For the Forms API, make sure that the semicolons are also URL encoded:

...&property_name=value1%3Bvalue2%3Bvalue4