Bootstrapping error: Too few observations?

[Jon Hoefer]

. *Sensitivity check using Bootstrapping
. global x Family_Firm_Identifier

. global y ROA

.  
. global m Premium1DW

.  
. capture program drop bootm3

. program bootm3, rclass
  1.                
.                 global controls FirmAge FirmSize Growthopp Indebtedness i.SIC_2 i.Fiscal_Year
  2.                 reg $m $x $controls, vce(cluster GVKEY)
  3.                 matrix path1 = e(b)
  4.                 di path1[1,1]
  5.                 global bx1 path1[1,1]
  6.                                
.                 global controls FirmAge FirmSize Growthopp Indebtedness i.SIC_2 i.Fiscal_Year
  7.                 reg $y $x $m $controls, vce(cluster GVKEY)
  8.                 matrix path2 = e(b)
  9.                 di path2[1,2]
 10.                 global bm1 path2[1,2]  
 11.  
.                 return scalar ciemn1 = $bx1*$bm1
 12.  
. end

. bootstrap r(ciemn1), level(95) reps(500) seed(1): bootm3
(running bootm3 on estimation sample)

Bootstrap replications (500)
----+--- 1 ---+--- 2 ---+--- 3 ---+--- 4 ---+--- 5
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx    50
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   100
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   150
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   200
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   250
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   300
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   350
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   400
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   450
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   500
insufficient observations to compute bootstrap standard errors
no results will be saved
r(2000);

Dear all, I am running a bootstrapping code in order to determine the statistical significance of my indirect effect in a mediation analysis. The underlying model is a pooled OLS model in this case (I run Random effects with clustered standard errors, too. However this should not matter at this point I think). My Dataset is a panel dataset with 1777 observations over 22 years.
In this example, I have reduced the replications to 500, normally using 5000. Nevertheless, how comes I get no results at all? As a potentially helpful aside, Premium1DW = Mediator, has very few observations (approx. 100). When I run the same mediation with another mediation, that has 800 obversations, from 5000 replications approx. 2000 observations are successfully drawn. Thank you in advance for any advice / ideas / help.