We have released version 2.0 of One Step Checkout which changed the flow of Terms and Conditions (TOS).
This version is inherited TOS of Magento 2 default. Follow these steps to enable TOS.
Step 1: Enable TOS in One Step Checkout
Go to Admin > Mageplaza > One Step Chec
Step 2: Enable TOS in Magento 2 default
Go to Stores > Settings > Configuration > Sales > Checkout > Checkout Options > Enable Terms and Conditions : Yes
Step 3: Add Terms and Conditions
There is empty TOS in the Terms and Conditions list, now you have to add your TOS.
Admin > Stores > Settings > Terms and Conditions > Add New Condition
Fill the information as above then click Save Condition
Flush cache to make sure it is changed.