Presumably your Notebooks are not being saved in a Trusted Path. Start by reading the tutorial Notebook Security, and note:
If the notebook's directory is trusted, the notebook will be allowed
to automatically perform dynamic evaluations without alerting the
user.
If the notebook's directory is untrusted, the user will be alerted
upon any attempt by the notebook to perform dynamic evaluations.
By default, the TrustedPath option value contains [$InstallationDirectory
](http://reference.wolfram.com/language/ref/$InstallationDirectory.html), [`$BaseDirectory](http://reference.wolfram.com/language/ref/$BaseDirectory.html), and [
$UserBaseDirectory`](http://reference.wolfram.com/language/ref/$UserBaseDirectory.html) so that Wolfram System installation files and additional installed applications will be able to display dynamic content without alerting the user.
The tutorial also covers how to add a directory to this path. Run this code and click the button produced:
Button["Edit TrustedPath...",
FEPrivate`OptionDialog[$FrontEnd,
{"NotebookSecurityOptions", "TrustedPath"}],
Appearance -> {Automatic, "DialogBox"},
Evaluator -> Automatic, Method -> "Preemptive"]
Or see: How to add a trusted path in Mathematica?