New Member Registration - Email address is not being stored in the database

Juanita:

Sorry I forgot you are a newbie to javascripting.

This line

.eq("email", userEmail) < -- -- -- -- -- -- - ensure unique use of email 

Doesn’t work because it was me highlighting the changed test in your .eq(). If you remove everything to the right of the closing parenthesis (i.e. < – – – – – – - ensure unique use of email ) it should be fine
So the code should be:

.eq("email", userEmail)

The other thing I would do is handle the case where this test fails:

if (results.items.length === 0)

So you actually want to do something (at least for testing purposes if nothing else) on two other conditions. One condition is

 } else if (results.items.length > 1) {

In this case you have detected duplicate records with the same email address which is something you don’t want to happen and should have a consequence right?

the other condition is:

} else {   // Essentially this verifies a matching record

SO your code would look something like (note: something like not necessarily exactly like ;-)) this

// prompt the user to log in
wixUsers.promptLogin({ "mode": "login" })
.then((user) => {                 
    userId = user.id; 
    return user.getEmail(); 
}) 
.then((email) => {
    // check if there is an item for the user in the collection
    // PER JEROME'S SUGGESTION
    console.log('User Email Address is:'+email);
    userEmail = email;
    return wixData.query("Profile").eq("email", userEmail).find();
 }) 
 .then((results) => { 
     // if an item for the user is not found 
     // PER JEROME'S SUGGESTION
     console.log('Profile records returned for '+userEmail+' = 'results.items.length);
     if (results.items.length === 0) { 
         // create an item 
         const toInsert = { "_id": userId, "email": userEmail};
         // add the item to the collection
         wixData.insert("Profile", toInsert) 
         .catch((err) => {
             console.log(err); 
         });
     } else if (results.items.length > 1) {
         // You may want to do something else here    
         console.log('Oh no we have too many ['+results.items.length+'] Profile records for '+userEmail);
     } else {
         // In production code when you have finished debugging the page 
         // This else clause could be removed
         console.log('We have seen this user before and things are good!');
     }
     // update buttons accordingly 
     $w("#register").label = "Logout";
     $w("#showdashboard").show();
 }) 
 .catch((err) => {
     console.log(err);
 });