I've installed msp-recaptcha-18.104.22.168 in my Magento 2.2.6 installation and all works fine except for a glitch on the Checkout page.
On the Checkout page customers first see the "Review & Payments" section which contains an "Email Address" field. The email field has a listener which checks whether an entered email address belongs to an existing customer. If yes, a hidden Password field is made visible and we see the text "You already have an account with us. Sign in or continue as guest." and a Login button. However the reCaptcha widget is NOT displayed. Thus it is impossible to log in from here as the error message "Incorrect reCaptcha" always results.
In the top right corner of the Checkout page there is a "Sign In" popup which DOES contain the reCaptcha widget and works properly.
The MSP reCaptcha extension includes code to use the reCaptcha widget in the in-line Login case, but it's not working. Any workaround or solution would be really appreciated. After many hours I still cannot make it work. Thanks.