Sorry to be down on you, but the layout of your program is atrocious.
As a new programmer, this is one thing everyone should learn first. Tutorial 2
here here is on the very subject.
Using the method you have there, programs soon become tangled and very difficult to follow.
Here's your code tidied up a bit:
hide mouse
sync on: sync rate 40: Rem <<< You should turn Sync On before setting the rate!
make object box 1,1,1,3:color object 1,rgb(255,0,0)
make object box 2,1,1,3:color object 2,rgb(0,255,0)
make object sphere 3,1:color object 3,rgb(0,0,50)
make object box 4,10,0.1,10:position object 4,0,-0.55,0
balla#=90.0: Rem 90 is an integer!
do
print "Press escape to exit."
if ballx#>6 then player2score#=player2score#+1:ballx#=0:ballz#=0:balla#=270
if ballx#<-6 then player1score#=player1score#+1:ballx#=0:ballz#=0:balla#=90
set cursor 300,50:print player2score#
set cursor 320,50:print "-"
set cursor 340,50:print player1score#
ballx#=newxvalue(ballx#,balla#,0.3):ballz#=newzvalue(ballz#,balla#,0.3)
IF upkey()=1 and player1pos#<3.5 then player1pos#=player1pos#+0.5
IF downkey()=1 and player1pos#>-3.5 then player1pos#=player1pos#-0.5
if upkey()=1 and ballx#>4 and ballx#<4.5 then balla#=balla#+8
if downkey()=1 and ballx#>4 and ballx#<4.5 then balla#=balla#-8
IF keystate(17)=1 and player2pos#<3.5 then player2pos#=player2pos#+0.5
IF keystate(31)=1 and player2pos#>-3.5 then player2pos#=player2pos#-0.5
if keystate(17)=1 and ballx#<-4 and ballx#>-4.5 then balla#=balla#+8
if keystate(31)=1 and ballx#<-4 and ballx#>-4.5 then balla#=balla#-8
if ballx#>4 and ballx#<4.5 and ABS(player1pos#-ballz#)<1.5 then balla#=360-balla#
if ballx#<-4 and ballx#>-4.5 and ABS(player2pos#-ballz#)<1.5 then balla#=360-balla#
if ballz#>4 or ballz#<-4 then balla#=180-balla#
balla#=wrapvalue(balla#): Rem <<< What does this do?
position object 1,5,0,player1pos#:position object 2,-5,0,player2pos#
position object 3,ballx#,0,ballz#:yrotate object 3,balla#
position camera 0,10,-10:point camera 0,0,0
sync
loop
Both bats move - the left one uses W and S keys.
My guess is that you are pasting code from other programs into your own program. This is OK if you fully understand what the code does. If you don't, you are asking for trouble...
TDK_Man