Do you have the ParentForm primary key as a ForeignKey stored in the ChildForm ?

If you leave the record and come back does the Child information appear?

Yes, in this case The parent is MaintenanceID and the child is MaintenanceDetailID.  I have MaintenanceDetail as the the primary key in the Child Table and MaintenanceID as a foreign key.  When filling in information in the maintenanceID continuous subform, the MaintenanceID does not populate in the MaintenanceDetailT.  I cannot figure out what is wrong.

Two more things, no, it doesn't fill in after I close the window, and it seems that I am having this issue with all of my subform relations.  Seems like there is something fundamental I haven't done.  I have watched many videos on this and I think I have done everything I am supposed to do. I made the tables relational using Primary Key/ Foreign Key, I made the forms from the tables.  I opened up the parent form and dragged the subform onto it.  I verified the link master and and link child fields are the same.  Is there something I am not doing?

If Access can't determine the linking fields, which can happen if the fields are named differently as you have, then you have to manually link the fields in the subform properties.

In the form where you added the subform, click on the subform once.  The then look at the properties either under the Data tab or the All tab for the Link Master Field (That should be MaintenanceID) and the Link Child Fields (That should be MaintenanceDetailID).  If those are not filled in you will have to manually set them using the ... button.
  
If you want to name you fields like you have, you will have to get used to manually making the connection.
Personally I ALWAYS name the foreign key the same as the Primary Key in the parent table.  The only difference is that the foreign key is not an autonumber.  Just a number of type Long Integer.

As Scott suggested, click the "..." button to set the master and child fields (see picture below).  Sometimes the pop up will automatically make the right suggestion for you.

As long as your tables have the right data, the method above will work.  Parent and child tables should have data the look like below.  The parent table has one primary key field that is used to link it to the child table.  The child table usually has a two-field primary key as shown below:

Parent table:
ID (PK)   Field1
1         John
2         Jane
3         Joe
4         Juan

Child table:

ID (PK)   LineNum (PK)   Field1
1         1              John's first item
1         2              John's second item
1         3              John's third item
2         1              Jane's first item
2         2              Jane's second item
4         1              Juan's first item
4         2              Juan's second item
4         3              Juan's third item
4         4              Juan's fourth item

In table design, both the ID and LineNum fields should a "key" symbol next to them, indicating a two-column primary key.  That means the ID-LineNum combination should be unique.  Every table should have a primary key.  And this is how a child table's primary key should be.

Thanks for all the help!