Is it possible that it's something to do with Google Chrome? I use the following Apps and none of them are now opening!:
My Fitness pal, Pinterest, Instagram, In My Area, etc.
No links are opening the apps - they are defaulting to the web pages instead!
Does anyone know how to fix this issue?
Contact the MFP Support and tell them their latest app version stopped listening so-called "intent filter" for opening their app through the app links. Or install the previous version of their app from an APK arhive (i.e. apkmirror.com, or apkssl.cpm), and disable the auto-update fro MFP in the Google Play store.
Is it possible that it's something to do with Google Chrome?
Chrome is usually the default handler fo links, so if the respective receiving app stops listening the link open intent through the intent filter, the default app for all links will take over. If you think Chrome hijacked some of the app links by error, open Chrome in Android Settings » Apps » Chrome, select the option Set As Default (or Open as Default in some Android versions), and reset the defaults there. You will be then prompt to select the default app, the next time a link is called. However, the MFP app no-longer registers itself as a listener for the link calls, hence, you won't be able to select it, unless you use a different version than the current buggy one.