you missed a Carriage return/line feed
try this
SET TEXT FONT "Arial"
CLS
PRINT
PRINT "Welcome to your first Gab Lib."
PRINT
PRINT "Please guess the answer to the questions"
PRINT "to create your own unique, humorous story."
PRINT
REM Ask questions
INPUT "1. Enter a female name: ", NAME$
INPUT "2. Enter a skin problem: ", PROBLEM$
INPUT "3. Enter a body part: ", BODYPART1$
INPUT "4. Enter a negative emotion: ", EMOTION$
INPUT "5. Enter a plural noun: ", NOUN1$
INPUT "6. Enter a present tense verb: ", VERB1$
INPUT "7. Enter a time of day: ", TIME$
INPUT "8. Enter an object you can read: ", NOUN2$
INPUT "9. Enter a dollar amount: ", NUMBER$
INPUT "10. Enter a type of medicine: ", NOUN3$
INPUT "11. Enter a present tense verb: ", VERB2$
INPUT "12. Enter a positive emotion: ", EMOTION2$
INPUT "13. Enter a color: ", COLOR$
INPUT "14. Enter a noun: ", NOUN4$
INPUT "15. Enter a present tense verb: ", VERB3$
INPUT "16. Enter a past tense verb: ", VERBP$
INPUT "17. Enter a noun: ", NOUN5$
INPUT "18. Enter a present tense verb: ", VERB4$
REM Prepare to display story
SET TEXT SIZE 16
CLS
REM Calculate line height
offset = 480 / 30
REM First paragraph
a$ = "Once upon a time there was a princess named " + NAME$
CENTER TEXT 320, offset, a$
a$ = "who had a " + PROBLEM$ + " on her " + BODYPART1$ + "."
CENTER TEXT 320, offset * 2, a$
a$ = "This " + PROBLEM$ + " was so unsightly and caused"
CENTER TEXT 320, offset * 3, a$
a$ = "Princess " + NAME$ + " much " + EMOTION$ + "."
CENTER TEXT 320, offset * 4, a$
a$ = "For you see, none of the " + NOUN1$ + " in the"
CENTER TEXT 320, offset * 5, a$
a$ = "kingdom could stand to " + VERB1$ + " at her."
CENTER TEXT 320, offset * 6, a$
REM Second paragraph
a$ = "One night, a little after " + TIME$ + ", Princess " + NAME$
CENTER TEXT 320, offset * 8, a$
a$ = "was sitting in her room reading a " + NOUN2$ + "."
CENTER TEXT 320, offset * 9, a$
a$ = "The "+NOUN2$+" was about the cure for " + PROBLEM$ + "s."
CENTER TEXT 320, offset * 10, a$
a$ = "It had an address to mail " + NUMBER$ + " dollars for"
CENTER TEXT 320, offset * 11, a$
a$ = "a " + NOUN3$ + " to " + VERB2$ + " the " + PROBLEM$ + "."
CENTER TEXT 320, offset * 12, a$
a$ = "She sent off for the " + NOUN3$ + "."
CENTER TEXT 320, offset * 13, a$
REM Third paragraph
a$ = "The day the " + NOUN3$ + " arrived, Princess " + NAME$
CENTER TEXT 320, offset * 15, a$
a$ = "was " + EMOTION2$ + "."
CENTER TEXT 320, offset * 16, a$
a$ = "She ripped open the " + NOUN3$ + " and looked inside."
CENTER TEXT 320, offset * 17, a$
a$ = "There was some " + COLOR$ + " " + NOUN4$ + " in a"
CENTER TEXT 320, offset * 18, a$
a$ = "tube in the " + NOUN3$ + "."
CENTER TEXT 320, offset * 19, a$
a$ = "The instructions said to " + VERB3$ + " the " + NOUN4$
CENTER TEXT 320, offset * 20, a$
a$ = " on the " + PROBLEM$ + " and it would disappear."
CENTER TEXT 320, offset * 21, a$
REM Fourth paragraph
a$ = "Princess " + NAME$ + " " + VERBP$ + " the " + NOUN4$ + " all over"
CENTER TEXT 320, offset * 22, a$
a$ = "her " + BODYPART1$ + " and poof! her " + BODYPART1$ + " "
CENTER TEXT 320, offset * 23, a$
a$ = "disappeared."
CENTER TEXT 320, offset * 24, a$
a$ = "The moral of this " + NOUN5$ + " is to follow directions"
CENTER TEXT 320, offset * 25, a$
a$ = "or you will not be able to " + VERB4$ + " the consequences."
CENTER TEXT 320, offset * 26, a$
REM Wait for user to press a key
WAIT KEY
END
it was at the line you said, the line ended and instead of an ENTER, then next Center Text statement was on the same line - look at your code again, you'll see it
-RUST-
"What the... Mooooooooooo!"